Deyue Yan

Over the past 15 years, hyperbranched polymers have received much attention due to their unique chemical and physical properties as well as their potential applications in coatings, additives, drug and gene delivery, macromolecular building blocks, nanotechnology, and supramolecular science. Hyperbranched polymers can be prepared by means of single-monomer methodology (SMM) and double-monomer methodology (DMM). In SMM, the polymerization of an ABn or latent ABn monomer leads to hyperbranched macromolecules. SMM consists of at least four components: (1) polycondensation of ABn monomers; (2) self-condensing vinyl polymerization; (3) self-condensing ring-opening polymerization; (4) proton-transfer polymerization. In DMM, direct polymerization of two suitable monomers or a monomer pair gives rise to hyperbranched polymers. A classical example of DMM, the polymerization of A2 and Bn (n>2) monomers, is well known. Recently, a novel DMM based on the in situ formation of ABn intermediates from specific monomer pairs has been developed. This form of DMM is designated as ‘couple-monomer methodology’ (CMM) to clearly represent the method of polymerization. Many commercially available chemicals can be used as the monomers in these systems, which should extend the availability and accessibility of hyperbranched polymers with various new end groups, architectures and properties. Because a number of comprehensive reviews have been published on SMM, research involving DMM is emphasized here. In addition, recent developments in the modification, functionalization and application of hyperbranched polymers are described.

The in situ ATRP (atom transfer radical polymerization) "grafting from" approach was successfully applied to graft poly(methyl methacrylate) (PMMA) onto the convex surfaces of multiwalled carbon nanotubes (MWNT). The thickness of the coated polymer layers can be conveniently controlled by the feed ratio of MMA to preliminarily functionalized MWNT (MWNT-Br). The resulting MWNT-based polymer brushes were characterized and confirmed with FTIR, 1H NMR, SEM, TEM, and TGA. Moreover, the approach has been extended to the copolymerization system, affording novel hybrid core-shell nanoobjects with MWNT as the core and amphiphilic poly(methyl methacrylate)-block-poly(hydroxyethyl methacrylate) (PMMA-b-PHEMA) as the shell. The approach presented here may open an avenue for exploring and preparing novel carbon nanotubes-based nanomaterials and molecular devices with tailor-made structure, architecture, and properties.

All drugs for cancer therapy face several transportation barriers on their tortuous journey to the action sites. To overcome these barriers, an effective drug delivery system for cancer therapy is imperative. Here, we develop a drug self-delivery system for cancer therapy, in which anticancer drugs can be delivered by themselves without any carriers. To demonstrate this unique approach, an amphiphilic drug–drug conjugate (ADDC) has been synthesized from the hydrophilic anticancer drug irinotecan (Ir) and the hydrophobic anticancer drug chlorambucil (Cb) via a hydrolyzable ester linkage. The amphiphilic Ir–Cb conjugate self-assembles into nanoparticles in water and exhibits longer blood retention half-life compared with the free drugs, which facilitates the accumulation of drugs in tumor tissues and promotes their cellular uptake. A benefit of the nanoscale characteristics of the Ir–Cb ADDC nanoparticles is that the multidrug resistance (MDR) of tumor cells can be overcome efficiently. After cellular internalization, the ester bond between hydrophilic and hydrophobic drugs undergoes hydrolysis to release free Ir and Cb, resulting in an excellent anticancer activity in vitro and in vivo.

Abstract Hyperbranched polymers (HBPs) are highly branched macromolecules with a three‐dimensional dendritic architecture. Due to their unique topological structure and interesting physical/chemical properties, HBPs have attracted wide attention from both academia and industry. In this paper, the recent developments in HBP self‐assembly and their biomedical applications have been comprehensively reviewed. Many delicate supramolecular structures from zero‐dimension (0D) to three‐dimension (3D), such as micelles, fibers, tubes, vesicles, membranes, large compound vesicles and physical gels, have been prepared through the solution or interfacial self‐assembly of amphiphilic HBPs. In addition, these supramolecular structures have shown promising applications in the biomedical areas including drug delivery, protein purification/detection/delivery, gene transfection, antibacterial/antifouling materials and cytomimetic chemistry. Such developments promote the interdiscipline researches among surpramolecular chemistry, biomedical chemistry, nano­technology and functional materials.

The macroscopic molecular self-assembly of an amphiphilic hyperbranched copolymer in acetone generated multiwalled tubes millimeters in diameter and centimeters in length. The thickness of the tube walls approaches 400 nanometers, and the walls have an inhomogeneous lamella structure that alternates between ordered hydrophilic domains and amorphous, partly irregular hydrophilic domains.

Herein, we report a novel Janus particle and supramolecular block copolymer consisting of two chemically distinct hyperbranched polymers, which is coined as Janus hyperbranched polymer. It is constructed by the noncovalent coupling between a hydrophobic hyperbranched poly(3-ethyl-3-oxetanemethanol) with an apex of an azobenzene (AZO) group and a hydrophilic hyperbranched polyglycerol with an apex of a β-cyclodextrin (CD) group through the specific AZO/CD host–guest interactions. Such an amphiphilic supramolecular polymer resembles a tree together with its root very well in the architecture and can further self-assemble into unilamellar bilayer vesicles with narrow size distribution, which disassembles reversibly under the irradiation of UV light due to the trans-to-cis isomerization of the AZO groups. In addition, the obtained vesicles could further aggregate into colloidal crystal-like close-packed arrays under freeze-drying conditions. The dynamics and mechanism for the self-assembly of vesicles as well as the bilayer structure have been disclosed by a dissipative particle dynamics simulation.

A series of colloid silver or gold nanoparticles (AgNPs or AuNPs) were successfully prepared by in situ reduction and stabilization of hyperbranched poly(amidoamine) with terminal dimethylamine groups (HPAMAM-N(CH(3))(2)) in water, and they all exhibited highly antimicrobial activity. The particle size could be controlled easily by adjusting the molar ratio of N/Ag (or N/Au) in feed. When the molar ratio was 2, some aggregates of the nanoparticles separated from the colloidal solution, which showed some limited antimicrobial activity with the bacterial inhibition ratio of below 15%. As the molar ratio increased from 10 to 30, the average particle diameters decreased (from ca. 7.1 to 1.0 nm for AgNPs and from ca. 7.7 to 3.9 nm for AuNPs, respectively) and they all showed high dispersion stability and excellent antimicrobial efficiency. All the bacterial inhibition ratios reached up to ca. 98% at the low silver content of ca. 2.0 microg/mL or at the low gold content of ca. 2.8 microg/mL. The AgNPs or AuNPs with smaller particle size can provide much more effective contact surface with the bacteria, thus enhancing their antimicrobial efficiency. Besides, the cationic HPAMAM-N(CH(3))(2) can also do some contribution to the antimicrobial activity through the strong ionic interaction with the bacteria.

This feature article describes the supramolecular self-assembly of hyperbranched polymers (HBPs), including the progress, unique characteristics and future perspectives. HBPs are irregular in molecular structure compared with that of linear block copolymers and dendrimers. However, similar to these well-defined polymer tectons, HBPs have displayed great potential to be excellent precursors in solution self-assembly, interfacial self-assembly and hybrid self-assembly. Many impressive supramolecular aggregates and hybrids at all scales and dimensions, such as macroscopic tubes, micro- or nano-vesicles, fibers, spherical micelles and honeycomb films, have been generated. In addition, HBPs also demonstrate unique characteristics or advantages in supramolecular self-assembly behaviours, including controllable morphologies and structures, special properties, characteristic self-assembly mechanism and facile functionalization process. Although still being at the early stage, self-assembly of HBPs has provided a new avenue for the development of supramolecular chemistry.

Hyperbranched polymers (HBPs), an important subclass of dendritic macromolecules, are highly branched, three-dimensional globular nanopolymeric architectures. Attractive features like highly branched topological structures, adequate spatial cavities, numerous terminal functional groups and convenient synthetic procedures distinguish them from the available polymers (the linear, branched, and crosslinking polymers). Due to their unique physical/chemical properties, applications of HBPs have been explored in a large variety of fields. In particular, HBPs exhibit unique advantages in the biological and biomedical systems and devices. Firstly, the way to prepare HBPs usually only involves simple one-pot reactions and avoids the complicated synthesis and purification procedures, which makes the manufacturing process more convenient, thus reducing production costs. Secondly, the large number of end-groups of HBPs provides a platform for conjugation of the functional moieties and can also be employed to tailor-make the properties of HBPs, enhancing their versatility in biological applications. Thirdly, HBPs possess excellent biocompatibility and biodegradability, controlled responsive nature, and ability to incorporate a multiple array of guest molecules through covalent or noncovalent approaches. All of these features of HBPs are of great significance for designing and producing biomaterials. To date, significant progress has been made for the HBPs in solving some of the fundamental and technical questions toward their bioapplications. The present review highlights the contribution of HBPs to biological and biomedical fields with intent to aid the researchers in exploring HBPs for bioapplications.

This <italic>tutorial review</italic> summarizes the first 10 years of work on hyperbranched polymer vesicles from syntheses, self-assembly, and properties to applications.

Abstract Cancer cells in hypoxic tumors are remarkably resistant to photodynamic therapy. Here, we hypothesize that an oxygen and Pt(II) self-generating multifunctional nanocomposite could reverse the hypoxia-triggered PDT resistance. The nanocomposite contains Pt(IV) and chlorin e6, in which upconversion nanoparticles are loaded to convert 980 nm near-infrared light into 365 nm and 660 nm emissions. Upon accumulation at the tumor site, a 980 nm laser is used to trigger the nanocomposite to generate O 2 for consumption in the PDT process and to produce cytotoxic reactive oxygen species. The composite also releases active Pt(II) for synergistic photo-chemo therapy to enhance antitumor efficiency. The oxygen and Pt(II) self-generating prodrug is shown to have high potential to inhibit tumors out of the range of UV light, to overcome the hypoxia-triggered PDT resistance and significantly improve anticancer efficacy by the synergistic PDT-chemotherapy.

A linear-hyperbranched supramolecular amphiphile was synthesized through the noncovalent coupling of adamantane-functionalized long alkyl chain (AD-Cn, n = 12, 18, 30) and hyperbranched polyglycerol grafted from β-cyclodextrin (CD-g-HPG) by the specific AD/CD host–guest interactions. The obtained supramolecular Cn-b-HPGs self-assembled into unilamellar vesicles with great ductility that could be disassembled readily under a competitive host of β-CD.

Superhydrophobic and superoleophilic graphene/polyvinylidene fluoride (G/PVDF) aerogels were prepared by solvothermal reduction of the graphene oxide and PVDF mixed dispersions. The chemical reduction of the graphene oxide component was verified by FT-IR, XRD, XPS, Raman spectroscopy and TGA. The as-prepared aerogel showed high specific surface area, eminent absorption capacity for oils and organic solvents, superior water repelling ability, excellent absorption recyclability, and considerable mechanical properties. Therefore, this kind of aerogel is a promising material for oil–water separation, oil spill cleanup and recovery of organic solvents. Moreover, this work paved a facile way to fabricate superhydrophobic and superoleophilic graphene-based aerogels with graphene oxide and a hydrophobic polymer.

Self-assembly of amphiphilic hyperbranched polymers (HBPs) is a newly emerging research area and has attracted increasing attention due to the great advantages in biomedical applications. This tutorial review focuses on the self-assembly of biocompatible or biodegradable amphiphilic HBPs and their cytomimetic applications, and specialities or advantages therein owing to the hyperbranched structure have also been summarized. As shown here, various supramolecular structures including micelles, vesicles, tubes, fibers and films have been prepared through the primary self-assembly processes. The primary self-assemblies can be further assembled into more complex structures through hierachical self-assembly processes. Besides, the hyperbranched polymer vesicles have demonstrated great potential to be used as model membranes to mimic cellular behaviors, such as fusion, fission and cell aggregation. Other biomedical applications of HBPs as well as their self-assemblies are also briefly summarized.

Benefiting from their responsiveness and adaptability, the stimuli-responsive polymers have been widely investigated and exploited in the various fields, such as environmental monitoring, electronics, photonics, controlled drug delivery, medical imaging and diagnostics. These potential applications have greatly promoted the development of advanced functional materials, and meanwhile set higher requirements for the smart materials in the aspects of the spatial structures, diverse linkages and variable functions. However, the linear functional polymers can not satisfy all the requirements of the multi-dimensional molecular design and acute sensitiveness due to the architectural limitation. Accordingly, stimuli-responsive hyperbranched polymers (HBPs) have been drawing more and more attention in recent years owing to their unique globular void-containing topological structure featured with a large number of terminal functional groups and branches, lower solution or melt viscosity, and better solubility. Therefore, design and synthesis of stimuli-responsive HBPs provide a robust tool for controlling the structure transition and creating the hierarchical sensitivity driven by different triggers. In this review, the developments and recent advances of preparation procedures, performance control and promising applications of various stimuli-responsive HBPs have been comprehensively summarized. Besides, the developing trend of stimuli-responsive HBPs is also discussed. It can be found that stimuli-responsive HBPs with different synthetic strategies and diverse performances have manifested more and more versatile applications.

Guest editors Anne-Marie Caminade, Deyue Yan and David K. Smith introduce the Dendrimers and Hyperbranched Polymers issue of <italic>Chemical Society Reviews</italic>

A superhydrophobic neat graphene aerogel that exhibited excellent properties for oil-absorption and oil–water separation has been fabricated for the first time.

To enhance the electron transfer within the covalent organic frameworks (COFs), we obtained a nanocomposite of conductive poly(3,4-ethylenedioxythiophene) (PEDOT) and redox-active AQ-COF by performing a facile in situ solid-state polymerization inside the nanochannels of COFs. The PEDOT chains functioned like electron highways within the nanochannels, resulting in a PEDOT@AQ-COF nanocomposite with an excellent electrical conductivity of 1.1 S cm–1 and a remarkably improved performance in faradaic energy storage. The all-organic PEDOT@AQ-COF electrode showed specific capacitance as high as 1663 F g–1 (at 1 A g–1), ultrafast charge/discharge rate performance (998 F g–1 at 500 A g–1), and excellent stability for 10 000 cycles. This research demonstrates a promising strategy for increasing the conductivity of COF-based materials and broadening their applications.

The poor compatibility with Li metal and electrolyte oxidation stability preclude the utilization of commercial ester‐based electrolytes for high‐voltage lithium metal batteries. This work proposes a quasi‐localized high‐concentration electrolyte ( q‐ LHCE) by partially replacing solvents in conventional LiPF 6 based carbonated electrolyte with fluorinated analogs (fluoroethylene carbonate (FEC), 2,2,2‐trifluoroethyl methyl carbonate (FEMC)) with weakly‐solvating ability. The q‐ LHCE enables the formation of an anion‐rich solvation sheath, which functions like LHCE but differs in the partial participation of weakly‐solvating cosolvent in the solvation structure. With this optimized electrolyte, inorganic‐dominated solid electrolyte interphases are achieved on both the cathode and anode, leading to uniform Li deposition, suppressed electrolyte decomposition and cathode deterioration. Consequently, q‐ LHCE supports stable cycling of Li | LiCoO 2 (≈3.5 mAh cm −2 ) cells at 4.5 V under the whole climate range (from −20 to 45 °C) with limited Li consumption. A practical ampere‐hour level graphite | LiCoO 2 pouch cell at 4.5 V and aggressive Li | LiNi 0.5 Mn 1.5 O 4 cell at 5.0 V with excellent capacity retention further reveals the effectiveness of q‐ LHCE. The refinement of old‐fashioned carbonate electrolytes provides new perspectives toward practical high‐voltage battery systems.

Dynamical control of perfect absorption plays an indispensable role in optical switch and modulators. However, it always suffers from the limited modulation range, small depth, and susceptible absorption efficiencies. Here, we propose a new strategy based on Friedrich–Wintgen bound states in the continuum (F–W BICs) to realize a tunable perfect absorber with large dynamic modulation range. For proof of concept, we demonstrate a pentaband ultrahigh absorption system consisting of graphene gratings and graphene sheets through elaborately tuning F–W BIC. The nature of the F–W BIC arises from the destructive interference between Fabry–Perot resonance and guided mode resonance modes in the coherent phase-matching condition. The radiation channels are avoided from crossing. The BIC can be dynamically modulated by engineering the Fermi level of graphene gratings, which breaks the traditional modulation methods with an incidence angle. Remarkably, the perfect absorber with this F–W BIC approach achieves the largest modulation range of up to 3.5 THz. We believe that this work provides a new way to dynamically engineer perfect absorption and stimulates the development of multiband ultracompact devices.

Using a modified definition, the average degree of branching, , the fraction of branchpoints, , as well as the fractions of various structural units are calculated as a function of conversion of double bonds for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (or “inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The results are compared to those for the polycondensation of AB2-type monomers. At full conversion, is somewhat smaller for SCVP ( ∞ ≈ 0.465) than for AB2 systems ( ∞ = 0.5). There are two kinds of linear groups in SCVP whereas there is only one kind in AB2 systems. Since there are two different active centers in SCVP, i.e., initiating B* and propagating A* centers, the effect of nonequal reactivities on is also discussed. At a reactivity ratio of the two kinds of active centers, r = kA/kB ≈ 2.59, a maximum value of ∞ = 0.5 is reached. For the limiting case r << 1, a linear polymer resembling a polycondensate will be formed whereas for r >> 1 a weakly branched vinyl polymer is expected. NMR experiments allow for the determination of reactivity ratio r.

A core−shell hybrid nanostructure, possessing a hard backbone of multiwalled carbon nanotube (MWNT) and a soft shell of brushlike polystyrene (PS), was successfully prepared by in situ atom transfer radical polymerization (ATRP), using Cu(I)Br/N,N,N',N'',N''-pentmethyldiethylenetriamine (PMDETA) as the catalyst, at 100 °C in diphenyl ether solution. The molecular weight of PS was well controlled, as was the thickness of the shell layer. TEM images of the samples provided direct evidence for the formation of a core−shell structure, i.e., the MWNT coated with polymer layer. FTIR, 1H NMR, SEM, and TGA were used to determine the chemical structure, morphology, and the grafted PS quantities of the resulting products. To further establish the covalent linkage between PS and MWNT moieties, the resulting PS-functionalized MWNTs were defunctionalized by hydrolysis or by thermal decomposition. Comparative studies, based on TEM and SEM images between the PS-functionalized and chemically defunctionalized MWNT samples, also revealed the covalent coating character. GPC analysis showed that the number-average molecular weight (Mn) of the grafted PS chains ranged from 5000 to 11 000 with a relatively broad polydispersity index (PDI, ca. 1.77−3.57). Further copolymerization of tert-butyl acrylate (tBA) with the PS-linked MWNTs as initiators was realized, illustrating that (1) the PS species is still "living" although the lower controllability of PDI and (2) acrylate-type monomers can be copolymerized with styrene-type ones on the sidewalls of the MWNT. We believe that achieving these hybrid objectives, on the basis of such simple grafting, will pave the way for the design, fabrication, optimization, and eventual application of more functional carbon nanotube-related nanomaterials.

An ill-defined hyperbranched multiarm copolymer (see picture) with a high hydrophilic fraction (>60 %) self-assembles in water to form giant polymer vesicles (branched polymersomes). The size of the branched polymersomes can be easily controlled by adjusting the hydrophilic fraction of the copolymer, with the average diameter of the larger branched polymersomes exceeding 100 μm. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2004/z460325_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The molecular weight distribution (MWD) and its moments are calculated for hyperbranched polymers formed by self-condensing vinyl polymerization (SCVP) of monomers (“inimers”) with the general structure AB*, where A is a vinyl group and B* is an initiating group. The calculated MWD is extremely broad, the polydispersity index (PDI) being equal to the number-average degree of polymerization: P̄w/P̄n = P̄n. It is twice as broad as that for the polycondensation of AB2 type monomers. If the fraction of unreacted monomer is not taken into account, the MWD becomes somewhat narrower, P̄‘w/P̄‘n ≈ 0.40P̄‘n. The kinetics of the polymerization process are first order with respect to the concentration of vinyl groups; P̄n, P̄w, and PDI increase exponentially with time. Comparison of the theoretical results with experimental data indicates that the rate constant of addition of an active center to a vinyl group decreases with increasing degree of polymerization. Since there are two different active centers in SCVP, namely initiating ones, B*, and propagating ones, A*, nonequal reactivities of the two centers (kA ≠ kB) have a strong effect on kinetics and MWD. The MWD narrows down to P̄w/P̄n = 2 for kA ≪ kB (corresponding to the common polycondensation of AB monomers) but broadens for kB > kA. Several deviations from ideal behavior are discussed.

A series of polyamide 1010 (PA1010 or nylon 1010) and multiwalled carbon nanotubes (MWNTs) composites were prepared by in situ polymerization of carboxylic acid-functionalized MWNTs (MWNT–COOH) and nylon monomer salts. Mechanical tensile tests and dynamic mechanical analysis (DMA) show that the Young modulus increases as the content of the nanotubes increases. Compared with pure PA1010, the Young's modulus and the storage modulus of MWNTs/PA1010 in situ composites are significantly improved by ca. 87.3% and 197% (at 0 °C), respectively, when the content of MWNTs is 30.0 wt%. The elongation at break of MWNTs/PA1010 composites decreases with increasing proportion of MWNTs. For the composites containing 1.0 wt% MWNTs, the Young modulus increases by ca. 27.4%, while the elongation at break only decreases by ca. 5.4% as compared with pure PA1010 prepared under the same experimental conditions. Compared with mechanical blending of MWNTs with pure PA1010, the in situ-prepared composites exhibit a much higher Young's modulus, indicating that the in situ polycondensation method improves mechanical strength of nanocomposites. Scanning electron microscopy (SEM) imaging showed that MWNTs on the fractured surfaces of the composites are uniformly dispersed and exhibit strong interfacial adhesion with the polymer matrix. Moreover, unique crystallization and melting behaviors for MWNTs/PA1010 in situ composites are observed using a combination of differential scanning calorimetry (DSC) and X-ray diffraction methods. It was shown that only the α-form crystals are observed in our MWNTs/PA1010 in situ composites. This result is quite different from PA1010/montmorillonite and PA6-clay composites, where both of α- and γ-form crystals were found.

CuO nanowires were prepared on the copper foil by thermal oxidation in air. The effect of annealing temperature and growth time on the morphology of the nanowires is investigated. It is found that the annealing temperature and the growth time play an important role in the morphology of CuO nanowires such as the density, the length and the diameter. The length and the density of nanowires increase with prolonging growth time; but if the time is too long, CuO crystallite grains form instead of nanowires. Annealing copper foils at lower or higher temperature, the density of nanowires is lower. For comparison, the Cu films on Si substrate deposited by direct current (dc) magnetron sputtering are oxidized, but we do not find large-scale of nanowires. The possible mechanism is also discussed for the growth of CuO nanowires.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetic Analysis of "Living" Polymerization Processes Exhibiting Slow Equilibria. 1. Degenerative Transfer (Direct Activity Exchange between Active and "Dormant" Species). Application to Group Transfer PolymerizationAxel H. E. Mueller, Rugang Zhuang, Deyue Yan, and Galina LitvinenkoCite this: Macromolecules 1995, 28, 12, 4326–4333Publication Date (Print):June 1, 1995Publication History Published online1 May 2002Published inissue 1 June 1995https://doi.org/10.1021/ma00116a040RIGHTS & PERMISSIONSArticle Views985Altmetric-Citations172LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (779 KB) Get e-Alerts Get e-Alerts

Oxime bonds dispersed in the backbones of the synthetic polymers, while young in the current spectrum of the biomedical application, are rapidly extending into their own niche. In the present work, oxime linkages were confirmed to be a robust tool for the design of pH-sensitive polymeric drug delivery systems. The triblock copolymer (PEG-OPCL-PEG) consisting of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic oxime-tethered polycaprolactone (OPCL) was successfully prepared by aminooxy terminals of OPCL ligating with aldehyde-terminated PEG (PEG-CHO). Owing to its amphiphilic architecture, PEG-OPCL-PEG self-assembled into the micelles in aqueous media, validated by the measurement of critical micelle concentration (CMC). The MTT assay showed that PEG-OPCL-PEG exhibited low cytotoxicity against NIH/3T3 normal cells. Doxorubicin (DOX) as a model drug was encapsulated into the PEG-OPCL-PEG micelles. Drug release study revealed that the DOX release from micelles was significantly accelerated at mildly acid pH of 5.0 compared to physiological pH of 7.4, suggesting the pH-responsive feature of the drug delivery systems with oxime linkages. Flow cytometry and confocal laser scanning microscopy (CLSM) measurements indicated that these DOX-loaded micelles were easily internalized by living cells. MTT assay against HeLa cancer cells showed DOX-loaded PEG-OPCL-PEG micelles had a high anticancer efficacy. All of these results demonstrate that these polymeric micelles self-assembled from oxime-tethered block copolymers are promising carriers for the pH-triggered intracellular delivery of hydrophobic anticancer drugs.

CeO2, Fe2O3, Fe2O3/Al2O3 and Ce–Fe mixed oxides with different Ce/Fe ratios were prepared and characterized using XRD, Raman, XPS, and H2–TPR techniques. The selective oxidation of methane to syngas using a gas–solid reaction was investigated at 850 °C. For binary Ce–Fe oxides, only small amounts of iron ions could be incorporated into the CeO2 lattice with the superfluous Fe2O3 remaining on the surface of the molecule. Chemical interactions between surface iron sites and the Ce–Fe solid solution strongly enhanced the reducibility of materials. Methane was found to adsorb and activate on the surface iron sites as carbonaceous species and hydrogen. Carbon deposition was selectively oxidized to CO by the release of activated oxygen from the CeO2 lattice. The activation rate of methane was dependent on the quality of dispersion of surface Fe species, while the oxygen mobility of the material dominated the CO formation rate. Hydrothermally prepared Ce0.7Fe0.3O2−δ showed high activity and selectivity during the successive production of syngas using repetitive redox processes (methane reduction/air re-oxidation). Both the dispersion of surface Fe2O3 and the formation of the Ce–Fe solid solution were enhanced by the redox treatment, which made the oxygen carrier more stable.

Abstract This work focused on the synthesis and aqueous self‐assembly of a series of novel hyperbranched star copolymers with a hyperbranched poly[3‐ethyl‐3‐(hydroxymethyl)oxetane] (HBPO) core and many linear poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) arms. The copolymers can synchronously form unimolecular micelles (around 10 nm) and large multimolecular micelles (around 100 nm) in water at room temperature. TEM measurements have provided direct evidence that the large micelles are a kind of multimicelle aggregates (MMAs) with the basic building units of unimolecular micelles. It is the first demonstration of the self‐assembly mechanism for the large multimolecular micelles generated from the solution self‐assembly of hyperbranched copolymers. magnified image

Novel redox-responsive polyphosphate nanosized assemblies based on amphiphilic hyperbranched multiarm copolyphosphates (HPHSEP-star-PEP(x)) with backbone redox-responsive, good biocompatibility, and biodegradability simultaneously have been designed and prepared successfully. The hydrophobic core and hydrophilic multiarm of HPHSEP-star-PEP(x) are composed of hyperbranched and linear polyphosphates, respectively. Benefiting from the amphiphilicity, HPHSEP-star-PEP(x) can self-assemble into spherical micellar nanoparticles in aqueous media with tunable size from about 70 to 100 nm via adjusting the molecular weight of PEP multiarm. Moreover, HPHSEP-star-PEP(x) micellar structure can be destructed under reductive environment and result in a triggered drug release behavior. The glutathione-mediated intracellular drug delivery was investigated against a HeLa human cervical carcinoma cell line, and the results indicate that doxorubicin-loaded (DOX-loaded) HPHSEP-star-PEP(x) micelles show higher cellular proliferation inhibition against glutathione monoester pretreated HeLa cells than that of the nonpretreated ones. In contrast, the DOX-loaded micelles exhibit lower inhibition against buthionine sulfoximine pretreated HeLa cells. These results suggest that such redox-responsive polyphosphate micelles can rapidly deliver anticancer drugs into the nuclei of tumor cells enhancing the inhibition of cell proliferation and provide a favorable platform to construct excellent drug delivery systems for cancer therapy.

A new type of biodegradable micelles for glutathione-mediated intracellular drug delivery was developed on the basis of an amphiphilic hyperbranched multiarm copolymer (H40-star-PLA-SS-PEP) with disulfide linkages between the hydrophobic polyester core and hydrophilic polyphosphate arms. The resulting copolymers were characterized by nuclear magnetic resonance (NMR), Fourier transformed infrared (FTIR), gel permeation chromatography (GPC), and differential scanning calorimeter (DSC) techniques. Benefiting from amphiphilic structure, H40-star-PLA-SS-PEP was able to self-assemble into micelles in aqueous solution with an average diameter of 70 nm. Moreover, the hydrophilic polyphosphate shell of these micelles could be detached under reduction-stimulus by in vitro evaluation, which resulted in a rapid drug release due to the destruction of micelle structure. The glutathione-mediated intracellular drug delivery was investigated against a Hela human cervical carcinoma cell line. Flow cytometry and confocal laser scanning microscopy (CLSM) measurements demonstrated that H40-star-PLA-SS-PEP micelles exhibited a faster drug release in glutathione monoester (GSH-OEt) pretreated Hela cells than that in the nonpretreated cells. Cytotoxicity assay of the doxorubicin-loaded (DOX-loaded) micelles indicated the higher cellular proliferation inhibition against 10 mM of GSH-OEt pretreated Hela cells than that of the nonpretreated ones. As expected, the DOX-loaded micelles showed lower inhibition against 0.1 mM of buthionine sulfoximine (BSO) pretreated Hela cells. These reduction-responsive and biodegradable micelles show a potential to improve the antitumor efficacy of hydrophobic chemotherapeutic drugs.

A new type of materials, the backbone-thermoresponsive hyperbranched polyether, was successfully synthesized by proton-transfer polymerization of 1,4-butanediol diglycidyl ether and various triols, and the lower critical solution temperature (LCST) values can be readily adjusted from 19.0 to 40.3 °C by changing the hydrophilic/hydrophobic balance of BDE and triols.

An in situ ring-opening polymerization strategy was employed to grow multihydroxyl dendritic macromolecules on the convex surfaces of multiwalled carbon nanotubes (MWNTs), affording novel one-dimensional (1D) molecular nanocomposites. The crude MWNTs were oxidized using 60% HNO3 and then reacted with thionyl chloride, resulting in MWNTs functionalized with chlorocarbonyl groups (MWNT-COCl). MWNT-COCl, when reacted with an excess of glycol, produced hydroxy-functionalized MWNT supported initiators (MWNT-OH). Using the MWNT-OH as the growth supporter and BF3·Et2O as catalyst, multihydroxy hyperbranched polyetherstreelike macromoleculeswere covalently grafted on the sidewalls and ends of MWNTs via in situ ring-opening polymerization of 3-ethyl-3-(hydroxymethyl)oxetane (EHOX). TGA measurements showed that the weight ratio of the as-grown hyperbranched polymers on the MWNT surfaces lay in the 20−87% range. The products were characterized by FTIR, NMR, DSC, TEM, and SEM. TEM indicates that the MWNTs are enveloped evenly by the hyperbranched molecules for samples with greater polymer coatings. The as-prepared nanocomposites exhibit relatively good dispersibility in polar solvents such as methanol, ethanol, DMF, and DMSO. Because of the fact that the hyperbranched macromolecules on the MWNTs contain numerous functional hydroxy groups on their periphery, the functionalized MWNTs can be further functionalized with the merits and advantages associated with dendritic polymers, which would result in a series of fascinating novel nanomaterials and nanodevices.

Membrane fusion is very important for the formation of many complex organs in metazoans throughout evolution, such as muscles, bones, and placentae. Lipid vesicles (liposomes) are frequently used as model membranes to study the fusion process. This work demonstrates for the first time the real-time membrane fusion of giant polymer vesicles by directly displaying a series of high-resolution and real-time transformation images of individual vesicles. The fusion process includes the sequential steps of membrane contact, forming the center wall, symmetric expansion of fusion pore and complete fusion, undergoing the intermediates of "8" shape with a protruding rim at the contact site, peanut (pear) shape, and oblate sphere. The vesicle swells during fusion, and the fusing vesicle only deforms in the neck domain around the fusion pore in the lateral direction, which verifies the importance of the lateral tension on the fusion pore at the vesicle deformation level. The successful fusion of the synthetic and protein-free polymer vesicles reported here also supports that vesicle proximity combined with membrane perturbation suffices to induce membrane fusion, and that the protein is not necessary for the fusion process.

Photo-responsive polymeric micelles have received increasing attention in both academic and industrial fields due to their efficient photo-sensitive nature and unique nanostructure. In view of the photo-reaction mechanism, photo-responsive polymeric micelles can be divided into five major types: (1) photoisomerization polymeric micelles, (2) photo-induced rearrangement polymeric micelles, (3) photocleavage polymeric micelles, (4) photo-induced crosslinkable polymeric micelles, and (5) photo-induced energy conversion polymeric micelles. This review highlights the recent advances of photo-responsive polymeric micelles, including the design, synthesis and applications in various biomedical fields. Especially, the influence of different photo-reaction mechanisms on the morphology, structure and properties of the polymeric micelles is emphasized. Finally, the possible future directions and perspectives in this emerging area are briefly discussed.

This study provided a facile and green method to prepare stable colloid silver nanoparticles in aqueous solution by utilizing the amine-terminated hyperbranched poly(amidoamine) (HPAMAM-NH2) as both stabilizer and reductant. The formation of silver nanoparticles was verified by FTIR, UV−vis, TEM, EDS, and XRD measurements. Monodispersed colloid silver nanoparticles with small particle sizes were obtained, and the average particle size could be effectively controlled from ca. 15 to 4 nm by simply adjusting the molar ratio of N/Ag in feed. The antibacterial activity of the HPAMAM-NH2/Ag nanocomposites was also investigated against Gram-positive and Gram-negative bacteria. They were able to efficiently inhibit the growth and multiplication of several bacteria, including Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella mobilis, and the bacterial inhibition ratio reached up to 95% at a low silver concentration of 2.7 μg/mL.

Graphene oxide was reduced by natural gallic acid at room temperature and upon heating. Gallic acid functioned as both a reductant and stabilizer during the reaction. The reduction of graphene oxide was verified by UV-vis, IR, Raman spectroscopy and XPS. Moreover, the reduced graphene oxide (rGO) exhibited the best dispersibility ever reported both in water and in organic solvents because of the gallic acid stabilizer. For example, the dispersibility of the rGO synthesized at room temperature is up to 1.2 mg ml−1 in water and 4 mg ml−1 in dimethylsulfoxide, respectively. This study offers a green approach to the mass preparation of rGO with excellent dispersibility.

Novel supramolecular copolymer micelles with stimuli-responsive abilities were successfully prepared through the complementary multiple hydrogen bonds of nucleobases and then applied for rapid intracellular release of drugs. First, both adenine-terminated poly(ε-caprolactone) (PCL-A) and uracil-terminated poly(ethylene glycol) (PEG-U) were synthesized. The supramolecular amphiphilic block copolymers (PCL-A:U-PEG) were formed based on multiple hydrogen bonding interactions between PCL-A and PEG-U. The micelles self-assembled from PCL-A:U-PEG were sufficiently stable in water but prone to fast aggregation in acidic condition due to the dynamic and sensitive nature of noncovalent interactions. The low cytotoxicity of supramolecular copolymer micelles was confirmed by MTT assay against NIH/3T3 normal cells. As a hydrophobic anticancer model drug, doxorubicin (DOX) was encapsulated into these supramolecular copolymer micelles. In vitro release studies demonstrated that the release of DOX from micelles was significantly faster at mildly acid pH of 5.0 compared to physiological pH. MTT assay against HeLa cancer cells showed DOX-loaded micelles had high anticancer efficacy. Hence, these supramolecular copolymer micelles based on the complementary multiple hydrogen bonds of nucleobases are very promising candidates for rapid controlled release of drugs.

Three kinds of complex oxides oxygen carriers (CeO2–Fe2O3, CeO2–ZrO2 and ZrO2–Fe2O3) were prepared and tested for the gas–solid reaction with methane in the absence of gaseous oxidant. These oxides were prepared by co-precipitation method and characterized by means of XRD, H2-TPR and Raman. The XRD measurement shows that Fe2O3 particles well disperse on ZrO2 surface and Ce–Zr solid solution forms in CeO2–ZrO2 sample. For CeO2–Fe2O3 sample, only a small part of Fe3+ has been incorporated into the ceria lattice to form solid solutions and the rest left on the surface of the oxides. Low reduction temperature and low lattice oxygen content are observed over ZrO2–Fe2O3 and CeO2–ZrO2 samples, respectively by H2-TPR experiments. On the other hand, CeO2–Fe2O3 shows a rather high reduction peak ascribed to the consuming of H2 by bulk CeO2, indicating high lattice oxygen content in CeO2–Fe2O3 complex oxides. The gas–solid reaction between methane and oxygen carriers are strongly affected by the reaction temperature and higher temperature is benefit to the methane oxidation. ZrO2–Fe2O3 sample shows evident methane combustion during the reducing of Fe2O3, and then the methane conversion is strongly enhanced by the reduced Fe species through catalytic cracking of methane. CeO2–ZrO2 complex oxides present a high activity for methane oxidation due to the formation of Ce–Zr solid solution, however, the low synthesis gas selectivity due to the high density of surface defects on Ce–Zr–O surface could also be observed. The highly selective synthesis gas (with H2/CO ratio of 2) can be obtained over CeO2–Fe2O3 oxygen carrier through gas–solid reaction at 800 °C. It is proposed that the dispersed Fe2O3 and Ce–Fe solid solution interact to contribute to the generation of synthesis gas. The reduced oxygen carrier could be re-oxidized by air and restored its initial state. The CeO2–Fe2O3 complex oxides maintained very high catalytic activity and structural stability in successive redox cycles. After a long period of successive redox cycles, there could be more solid solutions in the CeO2–Fe2O3 oxygen carrier, and that may be responsible for its favorable successive redox cycles performance.

Chemotherapy is an important modality in cancer treatment. The major challenge of recent works in this research field is to develop new types of smart nanocarriers that can respond selectively to cancer cell-specific conditions and realize rapid drug release in target cells. In the present study, a reactive oxygen species-responsive nanocarrier has been successfully self-assembled from an amphiphilic hyperbranched polymer consisting of alternative hydrophobic selenide groups and hydrophilic phosphate segments in the dendritic backbone. Because the hydrophobic selenide groups transformed into the hydrophilic selenone groups after oxidation under the exclusive oxidative microenvironment within cancer cells, the amphiphilic hyperbranched precursors become hydrophilic ones. As a result, the nanocarriers were rapidly disassembled in target cells, resulting in fast intracellular drug release. The hydrophilic products of oxidation can be degraded into harmless small molecular species via the enzymatic digestion of the phosphate segments and then eliminated by renal excretion. Meanwhile, the reactive selenium-containing nanocarrier possesses a potent intrinsic anticancer effect since selenium compounds can produce antitumor metabolites which induce apoptosis of cancer cells efficiently. Therefore, this type of therapeutic nanocarriers with a unique drug release mechanism based on an amphiphilic-to-hydrophilic transition provides a new platform for targeted drug delivery and combined therapy.

A multifunctional pH-sensitive superparamagnetic iron-oxide (SPIO) nanocomposite system was developed for simultaneous tumor magnetic resonance imaging (MRI) and therapy. Small-size SPIO nanoparticles were chemically bonded with antitumor drug doxorubicin (DOX) and biocompatible poly(ethylene glycol) (PEG) through pH-sensitive acylhydrazone linkages, resulting in the formation of SPIO nanocomposites with magnetic targeting and pH-sensitive properties. These DOX-conjugated SPIO nanocomposites exhibited not only good stability in aqueous solution but also high saturation magnetizations. Under an acidic environment, the DOX was quickly released from the SPIO nanocomposites due to the cleavage of pH-sensitive acylhydrazone linkages. With the help of magnetic field, the DOX-conjugated SPIO nanocomposites showed high cellular uptake, indicating their magnetic targeting property. Comparing to free DOX, the DOX-conjugated SPIO nanocomposites showed better antitumor effect under magnetic field. At the same time, the relaxivity value of these SPIO nanocomposites was higher than 146 s− 1 mM− 1 Fe, leading to ~ 4 times enhancement compared to that of free SPIO nanoparticles. As a negative contrast agent, these SPIO nanocomposites illustrated high resolution in MRI diagnosis of tumor-bearing mice. All of these results confirm that these pH-sensitive SPIO nanocomposites are promising hybrid materials for synergistic MRI diagnosis and tumor therapy.

Ce–Fe mixed oxides prepared by co-precipitation were used as oxygen carriers for converting methane into synthesis gas through gas–solid reactions. The structural evolution and reducibility of Ce–Fe oxygen carriers with calcination temperatures from 600 to 900 °C were investigated by XRD, BET, Raman, XPS and TPR techniques and correlated to their activity for methane selective oxidation. The Ce–Fe mixed oxides calcined at low temperatures (e.g., 600 °C) show abundant oxygen vacancies and high specific surface areas, which enhances the concentration of surface adsorbed oxygen and favors the complete oxidation of methane by means of gas–solid reactions. On the other hand, a calcination temperature of 900 °C results in serious sintering and militates against the formation of Ce–Fe solid solution, which brings about catalytic methane decomposition because of the low lattice oxygen mobility. A compromise calcination temperature at 800 °C favors the interaction between iron and cerium oxides, which could improve the lattice oxygen mobility of Ce–Fe oxygen carrier, leading to a high reactivity for methane selective oxidation. More importantly, the lattice oxygen mobility of the oxygen carrier is enhanced by the generation of oxygen vacancies after a repetitive redox treatment (methane reduction/air re-oxidation), which allows the Ce–Fe oxygen carrier to maintain a high activity and stability during the successive production of synthesis gas through a redox process.

Abstract Hyperbranched polymers (HBPs), invented at the end of 1980s, are one important subclass of the fourth generation macromolecular architectures following the linear, branched, and crosslinking polymers. Due to their unique topological structure and interesting physical/chemical properties, HBPs have attracted wide attention from both academia and industry. HBPs are composed of linear units, dendritic units, and terminal units. The degree of branching (DB), a term to describe the composition of these three structure units and thus the branching architecture of polymers, is one of the most important intrinsic parameters for HBPs. This review has summarized the effect of the DB on the physical and chemical properties of HBPs, including the rheological property, crystallization and melting behaviors, glass transition, thermal and hydrolytic degradations, phase characteristics, lower critical solution temperature phase transition, optoelectronic properties, encapsulation capability, self‐assembly behavior, biomedical applications, and so on. Such a structure and property relationship will build a bridge between the syntheses and applications of HBPs, especially in the application areas of functional materials, biomedical materials, and nanotechnology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1277–1286, 2011

A supramolecular drug delivery system has been developed via the self-assembly of a supramolecular amphiphilic polymer, which is constructed by the host–guest interaction of hydrophilic PEGylated calix[4]arene and hydrophobic photosensitizer chlorin e6. It provides a new strategy for the preparation of supramolecular polymeric micelles, and plays an important role in biological applications.

Abstract Graphene nanosheets offer intriguing electronic, thermal and mechanical properties and are expected to find a variety of applications in high‐performance nanocomposite materials. The great challenge of exfoliating and dispersing pristine graphite or graphene sheets in various solvents or matrices can be achieved by facilely and properly chemical functionalization of the carbon nanosheets. Here we reported an efficient way to functionalize graphene sheets with presynthesized polymer via a combination of atom transfer nitroxide radical coupling chemistry with the grafting‐onto strategy, which enable us to functionalize graphene sheets with well‐defined polymer synthesized via living radical polymerization. A radical scavenger species, 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO), was firstly anchored onto COOH groups on graphene oxide (GO) to afford TEMPO‐functionalized graphene sheets (GS‐TEMPO), meanwhile, the GO sheets were thermally reduced. Next, GS‐TEMPO reacted with Br‐terminated well‐defined poly( N ‐isopropylacrylamide) (PNIPAM) homopolymer, which was presynthesized by SET‐LRP, in the presence of CuBr/ N,N,N′,N′,N″ ‐pentamethyldiethylenetriamine to form PNIPAM‐graphene sheets (GS‐PNIPAM) nanocomposite in which the polymers were covalently linked onto the graphene via the alkoxyamine conjunction points. The PNIPAM‐modified graphene sheets are easily dispersible in organic solvents and water, and a temperature‐induced phase transition was founded in the water suspension of GS‐PNIPAM. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Controlled, deep breathing: Polymeric vesicles that exhibit reversible pH-induced “breathing” behavior accompanied by switchable fluorescence (see picture) were prepared through the aqueous self-assembly of an amphiphilic block copolymer. Mechanistic studies showed that this jellyfish-like breathing and light-emitting behavior originates from protonation- or deprotonation-induced changes in the conformation of the azobenzene chromophores. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Targeted drug delivery is a broadly applicable approach for cancer therapy. However, the nanocarrier-based targeted delivery system suffers from batch-to-batch variation, quality concerns and carrier-related toxicity issues. Thus, to develop a carrier-free targeted delivery system with nanoscale characteristics is very attractive. Here, a novel targeting small molecule nanodrug self-delivery system consisting of targeting ligand and chemotherapy drug was constructed, which combined the advantages of small molecules and nano-assemblies together and showed excellent targeting ability and long blood circulation time with well-defined structure, high drug loading ratio and on-demand drug release behavior. As a proof-of-concept, lactose (Lac) and doxorubicin (DOX) were chosen as the targeting ligand and chemotherapy drug, respectively. Lac and DOX were conjugated through a pH-responsive hydrazone group. For its intrinsic amphiphilic property, Lac-DOX conjugate could self-assemble into nanoparticles in water. Both in vitro and in vivo assays indicated that Lac-DOX nanoparticles exhibited enhanced anticancer activity and weak side effects. This novel active targeting nanodrug delivery system shows great potential in cancer therapy.

Currently, the major challenge for cancer treatment is to develop new types of smart nanocarriers that can efficiently retain the encapsulated drug during blood circulation and quickly release the drug in tumor cells under stimulation. In this study, the dual pH-/light-responsive cross-linked polymeric micelles (CPM) were successfully prepared by the self-assembly of amphiphilic glycol chitosan-o-nitrobenzyl succinate conjugates (GC-NBSCs) and then cross-linking with glutaraldehyde (GA), which was synthesized by grafting hydrophobic light-sensitive o-nitrobenzyl succinate (NBS) onto the main chain of hydrophilic glycol chitosan (GC). The GC-NBSC CPMs exhibited good biocompatibility according to the MTT assay against NIH/3T3 cells. The cell viability was maintained higher than 75% after 24 h incubation with CPMs even at a high concentration of 1.0 mg mL(-1). The hydrophobic anticancer drug camptothecin (CPT) was selected as a model drug and loaded into GC-NBSC CPMs. The results of in vitro evaluation showed that the encapsulated CPT could be quickly released at low pH with the light irradiation. Meanwhile, the CPT-loaded CPMs displayed a better cytotoxicity against MCF-7 cancer cells under UV irradiation, and IC50 of the loaded CPT was as low as 2.3 μg mL(-1), which was close to that of the free CPT (1.5 μg mL(-1)). Furthermore, the flow cytometry and confocal laser scanning microscopy (CLSM) measurements confirmed that the CPT-loaded CPMs could be internalized by MCF-7 cells efficiently and release CPT inside the tumor cells to enhance the inhibition of cell proliferation. Thereby, such excellent GC-NBSC CPMs provide a favorable platform to construct smart drug delivery systems (DDS) for cancer therapy.

Sleeping giants: As a mimic of cell agglomeration to form tissues, a novel vesicle aggregation process with the characteristic advantages of being highly efficient, light-responsive, reversible, large-scale, and stable is reported. Giant hyperbranched polymer vesicles (5–10 μm) are used as the building blocks (see scheme), and the vesicle aggregates can assemble and disassemble with alternating UV and Vis irradiation. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract Based on their structural similarity to natural nucleobases, nucleoside analogue therapeutics were integrated into DNA strands through conventional solid‐phase synthesis. By elaborately designing their sequences, floxuridine‐integrated DNA strands were synthesized and self‐assembled into well‐defined DNA polyhedra with definite drug‐loading ratios as well as tunable size and morphology. As a novel drug delivery system, these drug‐containing DNA polyhedra could ideally mimic the Trojan Horse to deliver chemotherapeutics into tumor cells and fight against cancer. Both in vitro and in vivo results demonstrate that the DNA Trojan horse with buckyball architecture exhibits superior anticancer capability over the free drug and other formulations. With precise control over the drug‐loading ratio and structure of the nanocarriers, the DNA Trojan horse may play an important role in anticancer treatment and exhibit great potential in translational nanomedicine.

A novel class of photo-responsive A2–B3 type supramolecular hyperbranched polymer with excellent optical properties can be polymerized and depolymerized reversibly by alternating UV/Vis light irradiation.

Up to now, limited tumor penetration and poor therapeutic efficiency of drug-loaded nanoparticles are still the major challenges in nanomedicines for cancer chemotherapy. In photodynamic therapy, photosensitizers are often used to generate cytotoxic reactive oxygen species to kill cancer cells. Here, we report a kind of ROS-responsive nanoparticles with light-triggered size-reducing for enhanced tumor penetration and in vivo drug delivery to improve therapeutic efficiency. The nanoparticles were constructed by the self-assembly of an amphiphilic hyperbranched polyphosphoester containing thioketal units and photosensitizers, which is synthesized through the self-condensing ring-opening polymerization of a novel cyclic phosphate monomer and then end-capped with photosensitizer Chlorin e6. These nanoparticles have an initial averaged diameter of ∼210 nm, which can be used as drug carriers to load camptothecin with relatively stable in blood circulation. The CPT-loaded nanoparticles can be concentrated in tumor tissues through the long blood circulation and enhanced permeability and retention effect. Upon 660 nm laser irradiation on tumor tissues, the Ce6s in nanoparticles can effectively generate ROS to kill cancer cells meanwhile cleave the thioketal units to sequentially reduce the size of nanoparticles, which facilitate them more efficient tumor penetration with a programmable release of CPT. Both in vitro and in vivo studies confirmed the above results. Such ROS-responsive nanoparticles with light-triggered size-reducing provided a feasible approach to improve drug tumor penetration and achieve satisfied therapeutic efficacy.

The porous silicon (PS) was produced by electrochemical etching of the P-type monocrystalline silicon in a double-tank cell and used as a substrate. The high-density zinc oxide nanosheets and nanorods were grown onto PS substrates by electrochemical deposition. The obtained ZnO nanostructures/PS products were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). The gas-sensing properties of ZnO nanostructures/PS composites to NO2 at different temperatures were studied. The result indicates that the addition of ZnO nanosheets greatly improve the gas-sensing properties of PS, especially at room temperature (RT). The ZnO nanosheets/PS sensor showed higher response values and gas selectivity, as well as much better response-recovery characteristics to NO2 gas compared with PS and ZnO nanorods/PS sensor due to its high specific surface area and special structural and morphological properties. The related mechanisms will be also discussed in this paper. This novel composite structure is of great significance for NO2 detection at room temperature.

A dandelion‐like supramolecular polymer (DSP) with a “sphere‐star‐parachute” topological structure consisting of a spherical hyperbranched core and many parachute‐like arms is constructed by the non‐covalent host–guest coupling between a cyclodextrin‐endcapped hyperbranched multi‐arm copolymer (host) and many functionalized adamantanes with each having three alkyl chain arms (guests). The obtained DSPs can further self‐assemble into nanotubes in water in a hierarchical way from vesicles to nanotubes through sequential vesicle aggregation and fusion steps. The nanotubes have a bilayer structure consisting of multiple “hydrophobic‐hyperbranched‐hydrophilic” layers. Such a structure is very useful for constructing a chlorosome‐like artificial aqueous light‐harvesting system, as demonstrated here, via the incorporation of hydrophobic 4‐(2‐hydroxyethylamino)‐7‐nitro‐2,1,3‐benzoxadiazole as donors inside the hyperbranched cores of the nanotubes and the hydrophilic Rhodamine B as the acceptors immobilized on the nanotube surfaces. This as‐prepared nanotube light harvesting system demonstrates unexpectedly high energy transfer efficiency (above 90%) in water. This extends supramolecular polymers with more complex topological structure, special self‐assembly behavior, and new functionality.

A facile strategy for the construction of supramolecular star-shaped ABC terpolymer was proposed and realized via the molecular recognition between β-cyclodextrin- (β-CD-) based host and adamantane- (AD-)modified guest. In the first step, β-CD with two different functional groups was prepared, which was further used to construct a diblock copolymer host via “click” reaction with alkynyl-poly(ethylene glycol) (alkynyl-PEG) and atom transfer radical polymerization (ATRP) of dimethylaminoethyl methacrylate (DMAEMA) monomer. On the other hand, the AD-modified polymeric guest was obtained by ATRP of methyl methacrylate (MMA) using an AD-modified initiator. Because of the molecular recognition between β-CDs and adamantyl moieties, the polymeric host and guest formed a star-shaped ABC miktoarm terpolymer via a simple mixing procedure. The resultant ABC miktoarm star-shaped terpolymer was characterized by two-dimensional NMR spectroscopy. This amphiphilic ABC miktoarm terpolymer could self-assemble into micelles in aqueous solution, and the reversible transition between assembly and disassembly of this supramolecular ABC miktoarm star terpolymer could be readily controlled by adding the competitive host or guest.

The best of both worlds: A novel amphiphilic homopolymer synthesized from a monomer consisting of a hydrophobic group (see picture, red) and a hydrophilic moiety (green) self-assembles in aqueous solution. The resulting micelles have a multi-core/shell structure and exhibit smart redox-responsive properties, thus providing a favorable drug delivery platform for cancer therapy. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

This work presents a highly efficient, broad spectrum and self-delivery anticancer agent, which is the hyperbranched polydiselenide (HPSe) consisting of alternative hydrophobic diselenide groups and hydrophilic phosphate segments in the backbone framework. The data of systematic evaluations demonstrate that HPSe is very potent to inhibit the proliferation of many forms of cancer cell. The dose of HPSe required for growth inhibition of 50% (IC50) in all of the tested cancer cell lines is within the concentration range between 1 and 2.5 μg mL−1 with the incubation time of 72 h. Furthermore, the amphiphilic HPSe can self-assembly into nanomicelles with an average diameter of 50 nm and spontaneously enter into tumor cells by the enhanced permeability and retention (EPR) effect. Besides, other hydrophobic anticancer drugs such as doxorubicin (DOX) can be encapsulated into HPSe micelles for combining therapy.

The utilization of nanotechnology for the delivery of a wide range of anticancer drugs has the potential to reduce adverse effects of free drugs and improve the anticancer efficacy. However, carrier materials and/or chemical modifications associated with drug delivery make it difficult for nanodrugs to achieve clinical translation and final Food and Drug Administration (FDA) approvals. We have discovered a molecular recognition strategy to directly assemble two FDA-approved small-molecule hydrophobic and hydrophilic anticancer drugs into well-defined, stable nanostructures with high and quantitative drug loading. Molecular dynamics simulations demonstrate that purine nucleoside analogue clofarabine and folate analogue raltitrexed can self-assemble into stable nanoparticles through molecular recognition. In vitro studies exemplify how the clofarabine:raltitrexed nanoparticles could greatly improve synergistic combination effects by arresting more G1 phase of the cell cycle and reducing intracellular deoxynucleotide pools. More importantly, the nanodrugs increase the blood retention half-life of the free drugs, improve accumulation of drugs in tumor sites, and promote the synergistic tumor suppression property in vivo.

Combination chemotherapy has been widely applied in cancer treatment; however, the cocktail administration of combination chemotherapy could cause the nonuniform biodistribution of anticancer agents, thus impairing the therapeutic efficacy. In the present study, to address this concern, we proposed a novel strategy of preparing self-assembled nanoparticles from amphiphilic drug-drug conjugate for synergistic combination chemotherapy. The conjugate was synthesized by two-step esterification of hydrophobic camptothecin (CPT) and hydrophilic floxuridine (FUDR) through a linker compound. Because of its amphiphilic nature, the CPT-FUDR conjugate self-assembled into stable nanoparticles which could simultaneously release fixed dosage of the two drugs in cancer cells. In vitro studies demonstrated synergistic anticancer efficacy of the CPT-FUDR nanoparticles including improved cell apoptosis, varied cell cycle arrest, as well as effective inhibition of cancer cell proliferation.

Combinatorial chemo and gene therapy provides a promising way to cure drug-resistant cancer, since the codelivered functional nucleic acids can regulate drug resistance genes, thus restoring sensitivity of the cells to chemotherapeutics. However, the dramatic chemical and physical differences between chemotherapeutics and nucleic acids greatly hinder the design and construction of an ideal drug delivery system (DDS) to achieve synergistic antitumor effects. Herein, we report a novel approach to synthesize a nanosized DDS using drug-integrated DNA with antisense sequences (termed "chemogene") to treat drug-resistant cancer. As a proof of concept, floxuridine (F), a typical nucleoside analog antitumor drug, was incorporated in the antisense sequence in the place of thymine (T) based on their structural similarity. After conjugation with polycaprolactone, a spherical nucleic acid (SNA)-like two-in-one chemogene can be self-assembled, which possesses the capabilities of rapid cell entry without the need for a transfection agent, efficient downregulation of drug resistance genes, and chronic release of chemotherapeutics for treating the drug-resistant tumors in both subcutaneous and orthotopic liver transplantation mouse models.

Two series of CeO2–Fe2O3 catalysts (CeO2–based and Fe2O3–supported oxides) with varying composition were synthesized by a hydrothermal method and characterized using various techniques. The comparison on the activity and thermal stability of different catalysts for low-temperature soot oxidation was also performed. The presence of both Ce–Fe–O solid solution and CeO2–Fe2O3 interaction were observed over the two types of catalysts. The oxygen vacancy in the solid solution is the crucial active site to facilitating the soot combustion over the CeO2–based samples. Small CeO2 nanoparticles are well dispersed on the Fe2O3–supported catalysts, which results in the formation of Fe–O–Ce species due to the strong CeO2–Fe2O3 interaction. The Fe–O–Ce species could achieve the coupling of the Ce4+–Ce3+ and Fe3+–Fe2+ couples in the CeO2–Fe2O3 interface, which is also identified as an active species for catalytic soot oxidation. The concentration of oxygen vacancy is closely related to the content of iron in ceria lattice, while the formation of Fe–O–Ce species strongly relies on the particle size of CeO2. It is also found that the oxygen vacancy is more active than the Fe–O–Ce species for soot oxidation, but it is very easy to decompose at high temperature, resulting in obvious deactivation of catalysts. By contrast, the Fe–O–Ce species is very stable under high-temperature treatments. For the fresh samples, the CeO2–based and Fe2O3–supported catalysts showed comparable catalytic activity. After long term aging at 800 °C, the loss on activity over the CeO2–based catalyst (Ce–Fe–O solid solution) is much higher than that over the Fe2O3–supported sample. The Fe2O3–supported catalysts are more suitable for practical application than the Ce–Fe–O solid solution.

Recent years have witnessed significant progress in the field of two-photon-activated photodynamic therapy (2P-PDT). However, the traditional photosensitizer (PS)-based 2P-PDT remains a critical challenge in clinics due to its low two-photon absorption (2PA) cross sections. Here, we propose that the therapeutic activity of current PSs can be enhanced through a combination of two-photon excited fluorescence resonance energy transfer (FRET) strategy and photothermal effect of near-infrared (NIR) light. A core-shell unimolecular micelle with a large two-photon-absorbing conjugated polymer core and thermoresponsive shell was constructed as a high two-photon light-harvesting material. After PSs were grafted onto the surface of a unimolecular micelle, the FRET process from the conjugated core to PSs could be readily switched "on" to kill cancer by the collapsed thermoresponsive shell due to the photothermal effect of NIR light. Such NIR-triggered FRET leads to an enhanced 2PA activity of the traditional PSs and, in turn, amplifies their cytotoxic singlet oxygen generation. Eventually, both in vitro and in vivo PDT efficiencies treated with the thermoresponsive micelles were dramatically enhanced under NIR light irradiation, as compared to pure PSs excited by traditional visible light. Such a facile and simple methodology for the enhancement of the photodynamic antitumor effect holds great promises for cancer therapy with further development.

Structurally well-defined graphene nanoribbons (GNRs) have attracted great interest as next-generation semiconductor materials.The functionalization of GNRs with polymeric side chains, which can widely broaden GNR-related studies on physiochemical properties and potential applications, has remained unexplored.In this work, we demonstrate the bottom-up solution synthesis of defect-free GNRs grafted with flexible poly(ethylene oxide) (PEO) chains.The GNR backbones possess an armchair edge structure with a width of 1.01.7 nm and mean lengths of 1560 nm, enabling near-infrared absorption and a low bandgap of 1.3 eV.Remarkably, the PEO grafting renders the GNRs superb dispersibility in common organic solvents, with a record concentration of 1 mg mL -1 (for GNR backbone) that is much higher than that (<0.01 mg mL -1 ) of reported GNRs.Moreover, the PEO-functionalized GNRs can be readily dispersed in water, accompanying with supramolecular helical nanowire formation.Scanning probe microscopy reveals raft-like self-assembled monolayers of uniform GNRs on graphite substrates.Thinfilm based field-effect transistors (FETs) of the GNRs exhibit a high carrier mobility of 0.3 cm 2 V -1 s -1 , manifesting promising application of the polymer-functionalized GNRs in electronic devices.

ABSTRACT Polyimides are a class of well‐known high‐performance polymers combined the excellent mechanical, electrical, and thermal properties and widely applied in many high‐tech fields. Traditional polyimides can only be processed in the state of soluble intermediates with a hazardous step of cyclodehydration and elimination of a nonvolatile polar solvent. Therefore, a great effort has been devoted to the development of soluble polyimides that can be processed in the full imidation state. The incorporation of side groups into the polyimide backbone is an efficient approach to resolve above problems with a little sacrifice of its inherent merits. The subtle variation of side groups in polyimide backbones has allowed researchers to tune their final properties. In particular, some special side groups can endow polyimides the specific property or functionality to broaden their application fields. In this article, we summarize the synthesis of polyimides with side groups in recent 20 years and further discuss the effect of side groups on their physical and specific properties. The future research directions of polyimides with side groups are also discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 533–559

Dendritic polymers are highly branched polymers with controllable structures, which possess a large population of terminal functional groups, low solution or melt viscosity, and good solubility. Their size, degree of branching and functionality can be adjusted and controlled through the synthetic procedures. These tunable structures correspond to application-related properties, such as biodegradability, biocompatibility, stimuli-responsiveness and self-assembly ability, which are the key points for theranostic applications, including chemotherapeutic theranostics, biotherapeutic theranostics, phototherapeutic theranostics, radiotherapeutic theranostics and combined therapeutic theranostics. Up to now, significant progress has been made for the dendritic polymers in solving some of the fundamental and technical questions toward their theranostic applications. In this review, we briefly summarize how to control the structures of dendritic polymers, the theranostics-related properties derived from their structures and their theranostics-related applications.

Abstract Combinatorial antitumor therapies using different combinations of drugs and genes are emerging as promising ways to overcome drug resistance, which is a major cause for the failure of cancer treatment. However, dramatic pharmacokinetic differences of drugs greatly impede their combined use in cancer therapy, raising the demand for drug delivery systems (DDSs) for tumor treatment. By employing fluorescent dithiomaleimide (DTM) as a linker, we conjugate two paclitaxel (PTX) molecules with a floxuridine (FdU)‐integrated antisense oligonucleotide (termed chemogene) to form a drug–chemogene conjugate. This PTX–chemogene conjugate can self‐assemble into a spherical nucleic acid (SNA)‐like micellular nanoparticle as a carrier‐free DDS, which knocks down the expression of P‐glycoprotein and subsequently releases FdU and PTX to exert a synergistic antitumor effect and greatly inhibit tumor growth.

A superhydrophobic graphene-based foam with outstanding elasticity was prepared for the first time, indicating excellent application prospects.

The combination of chemotherapy and photodynamic therapy (PDT) based on nanoparticles (NPs) has been extensively developed to improve the therapeutic effect and decrease the systemic toxicity of current treatments. However, overexpressed glutathione (GSH) in tumor cells efficiently scavenges singlet oxygens (1O2) generated from photosensitizers and results in the unsatisfactory efficacy of PDT. To address this obstacle, here we design H2O2-responsive polymer prodrug NPs with GSH-scavenger ([email protected](EG-a-CPBE) NPs) for chemo-photodynamic synergistic cancer therapy. They are constructed by the co-self-assembly of photosensitizer chlorin e6 (Ce6) and amphiphilic polymer prodrug P(EG-a-CPBE), which is synthesized from a hydrophilic alternating copolymer P(EG-a-PD) by conjugating hydrophobic anticancer drug chlorambucil (CB) via an H2O2-cleavable linker 4-(hydroxymethyl)phenylboronic acid (PBA). [email protected](EG-a-CPBE) NPs can efficiently prevent premature drug leakage in blood circulation because of the high stability of the PBA linker under the physiological environment and facilitate the delivery of Ce6 and CB to the tumor site after intravenous injection. Upon internalization of [email protected](EG-a-CPBE) NPs by tumor cells, PBA is cleaved rapidly triggered by endogenous H2O2 to release CB and Ce6. Ce6 can effectively generate abundant 1O2 under 660 nm light irradiation to synergistically kill cancer cells with CB. Concurrently, PBA can be transformed into a GSH-scavenger (quinine methide, QM) under intracellular H2O2 and prevent the depletion of 1O2, which induces the cooperatively strong oxidative stress and enhanced cancer cell apoptosis. Collectively, such H2O2-responsive polymer prodrug NPs loaded with photosensitizer provide a feasible approach to enhance chemo-photodynamic synergistic cancer treatment.

Abstract Aqueous zinc ion batteries (ZIBs) are troubled by the severe Zn dendrite growth and side reactions, manifesting as low coulombic efficiency and poor cyclic stability. Electrolyte engineering is regarded as an efficient method to improve Zn metal reversibility. Herein, a distinctive electrolyte regulation strategy is demonstrated for long‐lasting ZIBs through the construction of competitive solvation structures. In the composite aqueous system, the insoluble LiNO 3 in dimethyl carbonate (DMC) is introduced to outwit active water dissociation from Zn 2+ coordination environment, and the organic/anion‐enriched solvation structure enables the formation of a stable interface to effectively restrain adverse reactions. Distinctly, the Zn metal anode exhibits inhibited dendrite growth with high reversibility of plating/stripping processes over 1600 h with an exceptional cumulative capacity over 16 Ah cm −2 , an ultra‐long lifespan over high‐temperature (50 °C), and high discharge of depth (65%). Furthermore, the Zn || V 2 O 5 full battery can operate stably over 1000 cycles at 1 A g −1 . This work points a direction to effectively solve the major challenges of ZIBs through the collaborative construction of a regulated electrolyte environment and interfacial chemistry.

Dendrites growth and hydrogen evolution reaction of Zn anode greatly hinder the practical application of aqueous zinc ion batteries. Interface engineering strategies have attracted immense interest in addressing these challenges. Herein, a chemical and electrochemical method is proposed to synergistically weave a stable interface by introducing AgNO3 additive in conventional aqueous ZnSO4 electrolyte. The formed compact Ag layer acts as zincophilic sites, which is beneficial for zinc ion nucleation and growth. Consequently, the cell cycled in 2 M ZnSO4 with 3 mM AgNO3 electrolyte exhibits much more stable electrochemical properties than its counterpart. To be specific, the Zn || Zn half cell using the electrolyte with 3 mM AgNO3 shows reversible Zn plating/stripping behavior over 1350 h at 5.0 mA cm−2 with an ultra-low potential hysteresis. Moreover, Zn || V2O5 full cell using the electrolyte with 3 mM AgNO3 exhibits glorious rate capability and more stable cycling performance, attributing to the inhibited zinc dendrites growth by the weaved interfacial layer. This work sheds new light on improving the electrochemical performance of rechargeable batteries.

Digital synthetic polymers with uniform chain lengths and defined monomer sequences have recently become intriguing alternatives to traditional silicon-based information devices or natural biomacromolecules for data storage. The structural diversity of information-containing macromolecules endows the digital synthetic polymers with higher stability and storage density but less occupied space. Through subtly designing each unit of coded structure, the information can be readily encoded into digital synthetic polymers in a more economical scheme and more decodable, opening up new avenues for molecular digital data storage with high-level security. This tutorial review summarizes recent advances in salient features of digital synthetic polymers for data storage, including encoding, decoding, editing, erasing, encrypting, and repairing. The current challenges and outlook are finally discussed to offer potential solution guidance and new perspectives for the creation of next-generation digital synthetic polymers and broaden the scope of their applicability.

It is necessary to explore new mechanisms of plasmon-induced transparency (PIT) formation to achieve high-performance optical multifunction devices. Here, we introduced a symmetry-protected quasi bound states in the continuum (quasi-BIC) in the vicinity of the graphene plasmon resonance (GPR) mode to achieve a tunable plasmon-induced absorption (PIA) with 99.0 % and 99.4 %, which is the result of coupling between the bright modes. PIA supported by quasi-BIC has outstanding characteristics in both optical switching and slow light, with amplitude modulation depth up to 100 %, insertion loss below 0.04 dB, and group delay up to 10.3 ps. Significantly, it also solves the challenge that the absorption of the graphene system is reduced during dynamic modulation of electromagnetic waves. The dynamic modulation range of perfect absorption is up to 4.95 THz, which is much higher than any work that has been reported. We believe that the proposed structure provides a great reference for the future research direction of PIT and stimulates the development of high-performance multifunctional devices.

The conformational change of isotactic polypropylene (iPP) during the crystallization process has been carefully studied by Fourier transform infrared (FTIR) spectroscopy. The experimental measurements show that the iPP melt system is stable when the persistence length of helical sequences is less than 12 monomer units. As soon as the helix length exceeds 12 monomer units, the 31 helix conformation extends quickly and then crystallization occurs. These results are discussed in terms of Imai's microphase separation theory. It can be found that the experimental observation agrees very well with Imai's theory.

Two kinds of polyelectrolyte: polyacrylic acid (PAA) and poly(sodium 4-styrenesulfonate) (PSS), were grafted onto the convex surfaces of multiwalled carbon nanotubes (MWNTs) by surface-initiating ATRP (atom transfer radical polymerization) from the initiating sites previously anchored onto the convex surfaces of MWNTs. The grafted polyelectrolyte can be efficiently quantified by the feed ratio of monomer to MWNT-based macroinitiator, and the maximum amount of grafted polymer is higher than 55 wt%. The polyelectrolyte-coated MWNTs resembled core-shell structures justified by the TEM images of the samples obtained, which provided direct evidence for the covalent modification of MWNT. FTIR, 1H NMR and TGA were used to determine the chemical structure of the resulting products. Comparison of UV–Vis spectra demonstrated that the products were water-soluble, and that PSS was more effective for improving the water solubility of carbon nanotubes. Using the polyelectrolyte- and carboxylic acid-functionalized MWNTs as templates, and poly(2-(N,N-dimethylaminoethyl) methacrylate (PDMAEMA)/hyperbranched polysulfone amine (HPSA) and PSS as polycation and polyanion, respectively, layer-by-layer (LbL) electrostatic self-assembly was conducted in order to explore the application of the functionalized nanotubes. It was found that the functionalized MWNTs have a high efficiency for loading polyelectrolytes by the LbL approach (the adsorbed polymer quantity is higher than 10 wt% in one assembling step). TEM observations showed that the assembled polymer shell on the MWNT surfaces was very even and flat.

Novel thermosensitive polymer vesicles with controlled temperature-responsive phase transition at the lower critical solution temperature (LCST) varying from 8 to 81 degrees C were prepared via self-assembly of amphiphilic hyperbranched star copolymers having a hydrophobic hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many hydrophilic polyethylene oxide (PEO) arms. Real-time optical microscopic observation revealed that the polymer vesicles have undergone sequential morphology changes including enrichment, aggregation, fusion, and vesicle-to-membrane transformation near the LCST. Molecular-level investigation indicates that the LCST transition results from the decreasing water solubility of the polymer vesicles with increasing temperature based on the partial dehydration of the PEO vesicle corona. On the basis of these results, a LCST transition mechanism, in view of the molecular configuration, balance of hydrophilic and hydrophobic moieties, and the vesicle morphology transformations, was proposed. As far as we know, the work presented here is the first demonstration of thermosensitive vesicles based on PEO, and the finding may be useful to design the thermosensitive core-shell structures by introducing the PEO segments.

A series of novel hyperbranched multiarm copolyethers of PEHO-star-PPO with different molar ratios of PPO arms to PEHO cores (RA/C) were synthesized. NMR and SEC measurements confirm the molecular structure of PEHO-star-PPOs. Both glass transition temperature (Tg) and decomposition temperature (Td) of PEHO-star-PPO decrease with increasing RA/C. The self-assembly behavior of PEHO-star-PPO copolymers was investigated by TEM, SEM, DLS, etc. The results indicate that the ill-defined PEHO-star-PPO molecules could aggregate into large spherical micelles (over 100 nm) with controlled sizes, and the micelle size decreases as RA/C increases. The structure of the large micelles was explored by FT-IR, NMR, etc. Accordingly, a possible self-assembly process is put forward, and a new aggregate model termed as multimicelle aggregate (MMA) (Figure 9C) is suggested to explain the formation of the large micelles. In MMA model, the large micelles are the aggregates of small micelles associated by intermicellar interactions such as hydrogen bonds.

A new strategy for synthesis of hyperbranched polymers from commercially available A2 type and BB‘2 type monomers has been developed. In the first part of this series, hyperbranched polysulfone−amine with multiamino groups is prepared by polyaddition of 1-(2-aminoethyl)piperazine (BB‘2) to divinyl sulfone (A2) without any catalysts. The products are soluble in water and organic solvents such as N,N-dimethylformamide, chloroform, and N-methyl-2-pyrrolidone. The polymerization mechanism has been investigated with FTIR, HPLC, and MS. During the reaction, secondary amino groups of 1-(2-aminoethyl)piperazine react rapidly with vinyl groups of divinyl sulfone within 15 s, forming dominant dimers and some other species. The dimer can be considered as a new AB‘2 type of monomer. Further reactions among AB‘2 molecules and AB‘2 with other species result in the formation of hyperbranched polymers. The degree of branching of the resulting polymer is higher than 50%. No gelation occurs in solution polymerization when the A2 to BB‘2 ratio equals 1. Similarly, there is no gelation in solution polymerization if the feed ratio of A2 to BB‘2 is 3/2; however, gelation does occur when the resulting polymer is separated from the solution. There are both terminal amino groups and vinyl groups in the hyperbranched polysulfone−amine if the feed A2 to BB‘2 ratio is 3/2, which further react with each other in bulk state resulting in a cross-linked material. If the terminal amino groups are protected by hydrochloride acid in advance in the solution, then no gelation can be observed after the product is separated from the solution.

A fascinating nanoobject, amphiphilic polymer brushes with a hard core of multi-walled carbon nanotubes (MWNTs) and a relatively soft shell of polystyrene-block-poly(acrylic acid) (PS-b-PAA), was easily constructed by in situ atom transfer radical polymerization (ATRP) of styrene followed by tert-butyl acrylate on the modified convex surfaces of MWNTs (MWNT-PS) followed by hydrolysis of the grafted poly(tert-butyl acrylate) (PtBA) blocks. The structure and morphology of the as-prepared hybrid nanomaterials were characterized and confirmed by electron microscopy (TEM and SEM), nuclear magnetic resonance (NMR) spectrometry, and thermogravimetric analysis (TGA). The results showed that both styrene and acrylate types of ATRP-active vinyl monomers can be easily initiated and then propagated on the MWNT sidewalls via the in situ ATRP approach, and the length of the PtBA blocks increases with increasing tBA : MWNT-PS weight feed ratio. We believe that the breakthrough associated with formation of such a complex nanoobject would open a door for the fabrication of novel functional carbon nanotube-based nanomaterials or nanodevices with designable structure and tailor-made properties.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTPoly(N-isopropylacrylamide)-Coated Carbon Nanotubes: Temperature-Sensitive Molecular Nanohybrids in WaterHao Kong, Wenwen Li, Chao Gao, Deyue Yan, Yizheng Jin, David R. M. Walton, and Harold W. KrotoView Author Information College of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China, and Sussex Nanoscience and Nanotechnology Center (SNNC), University of Sussex, Brighton BN1 9QJ, U.K. Cite this: Macromolecules 2004, 37, 18, 6683–6686Publication Date (Web):August 4, 2004Publication History Received30 June 2004Published online4 August 2004Published inissue 1 September 2004https://doi.org/10.1021/ma048682oCopyright © 2004 American Chemical SocietyRequest reuse permissions Article Views1422Altmetric-Citations114LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (223 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Carbon nanotubes,Hydrophilicity,Polymers,Thermal properties,Thermoresponsive polymers Get e-Alerts

Angewandte Chemie International EditionVolume 44, Issue 21 p. 3223-3226 Communication Real-Time Membrane Fission of Giant Polymer Vesicles† Yongfeng Zhou Dr., Yongfeng Zhou Dr. College of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P.R. China, Fax: (+86) 21-5474-1297Search for more papers by this authorDeyue Yan Prof. Dr., Deyue Yan Prof. Dr. dyyan@sjtu.edu.cn College of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P.R. China, Fax: (+86) 21-5474-1297Search for more papers by this author Yongfeng Zhou Dr., Yongfeng Zhou Dr. College of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P.R. China, Fax: (+86) 21-5474-1297Search for more papers by this authorDeyue Yan Prof. Dr., Deyue Yan Prof. Dr. dyyan@sjtu.edu.cn College of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, P.R. China, Fax: (+86) 21-5474-1297Search for more papers by this author First published: 17 May 2005 https://doi.org/10.1002/anie.200462622Citations: 103 † Financial support from the National Natural Science Foundation of China (no. 20274024, 50233030) and from the basic research foundation of Shanghai Science and Technique Committee (no. 03 JC 14046, 04 JC 14057) is acknowledged. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Cooperation of mother and daughter vesicles, which are self-assembled from an ill-defined hyperbranched copolymer, leads to fission of the daughter membrane in a cytomimetic process (see picture; red: mother vesicle, green: daughter vesicle). This is the first example of giant polymer vesicles (5–200 μm) being used as model membranes. Citing Literature Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z462622_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume44, Issue21May 20, 2005Pages 3223-3226 RelatedInformation

In this Article, we have investigated the self-assembly of a series of amphiphilic hyperbranched star-block copolymers to form multicompartment micelles in acidic aqueous solution (pH 3.0) or in a dimethylformamide/water (pH 3.0) mixture. These hyperbranched star-block copolymers were prepared via oxyanion-initiated polymerization process, using hydroxyl-terminated hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HP) as a macroinitiator precursor with multi-reactive sites. It was turned into oxyanion end-capped macroinitiator through the reaction with potassium hydride, and followed by a sequential addition of 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA) and 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate (OFPMA). The resultant HP-star-PDMAEMA-b-POFPMA copolymers were characterized via 1H NMR, 19F NMR, and gel permeation chromatography (GPC). The analyses of transmission electron microscopy (TEM), dynamic light scattering (DLS), and microelectrophoresis confirmed that these copolymers could directly self-organize into supramolecular multicompartment micelles with different diameters, depending on the length of the PDMAEMA segment, which can be protonated in acidic aqueous medium. The measurement of the zeta potential gave further evidence of the aggregating structures for the multicompartment micelles.

A film to dye for: Honeycomb-patterned films have been fabricated by the self-assembly of amphiphilic hyperbranched poly(amidoamine) on solid substrates. The film thickness can be varied from the nanometer to micrometer scale simply by changing the concentration of the polymer solution. Luminescent films of different colors can be prepared by encapsulating various dyes into the polymer (see picture, R=(CH2)14CH3, red sphere=dye molecule). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z604429_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Hydrated porous birnessite MnO2 films were prepared on Si substrates and characterized in-depth by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). The as-prepared film is composed of a well-crystallized porous surface layer and one or more amorphous bottom layers. The morphology and structure of the film can be understood by the combined action of internal stress and conversion of the porous surface layer. The dynamic process of formation and conversion in the growth of porous surface layer is pointed out, which shows the transformation of reactants to amorphous bottom layers via the formation and conversion process of the porous surface layer. This result is of significant importance for increasing the utilization ratio of materials and for understanding basic physical and chemical processes of manganese oxide film growth under hydrothermal conditions.

A drug nanocarrier has been constructed through self-assembly of phospholipid analogous hyperbranched polymers (HPHEEP-alkyls) which contain a polar hyperbranched polyphosphate headgroup and many aliphatic tails. HPHEEP-alkyls were synthesized by self-condensing ring-opening polymerization of 2-(2-hydroxyethoxy)ethoxy-2-oxo-1,3,2-dioxaphospholane and then capped with palmitoyl chloride. Benefiting from the amphiphilic structure with the hydrophilic core and many hydrophobic tails, HPHEEP-alkyls were able to self-assemble into nanomicelles in aqueous media. Importantly, the size of the nanomicelles could be controlled conveniently from 98 to 215 nm by adjusting the capped fraction of the hydroxyl groups with hydrophobic palmityls. The excellent biocompatibility of these nanomicelles was confirmed by methyl tetrazolium assay and acridine orange/ethidium bromide double staining against COS-7 cells. Confocal laser scanning microscopy and flow cytometry analysis demonstrated their good cell permeability, i.e. these nanomicelles were easily internalized by vivid cells and mainly located in the cytoplasm rather than nucleolus. Chlorambucil-loaded nanomicelles were investigated for proliferation inhibition of a MCF-7 breast cancer cell line in vitro, and the chlorambucil dose required for 50% cellular growth inhibition was found to be 5 μg/mL. All of these results indicate that HPHEEP-alkyls nanomicelles can be used as safe and promising drug nanocarriers.

Abstract A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3‐ethyl‐3‐(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2‐(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self‐assembly. All the copolymers directly aggregated into core–shell unimolecular micelles (around 10 nm) and size‐controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1 H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature‐dependent release properties of HBPO‐ star ‐PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin‐loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668–681, 2008

A water-soluble hyperbranched polyphosphate (HPHEEP) was synthesized through the self-condensation ring-opening polymerization (SCROP) of 2-(2-hydroxyethoxy)ethoxy-2-oxo-1,3,2-dioxaphospholane (HEEP), and its suitability as a drug carrier was then evaluated in vitro. Methyl tetrazolium (MTT) and live/dead staining assays indicated that HPHEEP had excellent biocompatibility against COS-7 cells. The good biodegradability of HPHEEP was observed by NMR analysis, and the degradation products were nontoxic to COS-7 cells. Flow cytometry and confocal laser scanning microscopy analyses suggested that HPHEEP could be easily internalized by vivid cells and preferentially accumulated in the perinuclear region. Furthermore, a hydrophobic anticancer drug, chlorambucil, was used as a model drug and covalently bound to HPHEEP. The chlorambucil dose of the conjugate and free drug required for 50% cellular growth inhibition were 75 and 50 microg/mL, respectively, according to MTT assay against an MCF-7 breast cancer cell line in vitro. This high activity of the conjugate may be attributed to the biodegradability of HPHEEP so as to release the chlorambucil in cells. Therefore, on the basis of its biocompatibility and biodegradability, HPHEEP could provide a charming opportunity to design some excellent drug delivery systems for therapeutic applications.

Honeycomb-structured microporous films were self-assembled from a new type of multiarm copolymer, hyperbranched poly(3-ethyl-3-oxetanemethanol)-star-polystyrene (HBPO-star-PS). The precursor consisting of an HBPO core and a number of PS arms was synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. The microporous film was prepared by the evaporation of a chloroform solution of the precursor in a humid atmosphere (the so-called breath figure method). Compared to our former work, the hexagonally packed pores in the film were not interpenetrated and isolated from one another by the walls. The size of the pores could be controlled easily by changing the casting volume of the solution, the molecular weight and concentration of the polymer, and so forth. The water contact angle on the film surface indicated that the hydrophobicity of the film surface was significantly enhanced as a result of the formation of the porous structure.

Novel water-soluble dendritic-linear-brush-like triblock copolymer polyamidoamine-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (PAMAM-b-PDMAEMA-b-PPEGMA)-grafted superparamagnetic iron oxide nanoparticles (SPIONs) were successfully prepared via a two-step copper-mediated atom transfer radical polymerization (ATRP) method. The macroinitiators were immobilized on the surface of Fe(3)O(4) nanoparticles via effective ligand exchange of oleic acid with the propargyl focal point PAMAM-typed dendron (generation 2.0, denoted as propargyl-D(2.0)) containing four carboxyl acid end groups, following a click reaction with 2'-azidoethyl-2-bromoisobutylate (AEBIB). PDMAEMA and PPEGMA were grown gradually from nanoparticle surfaces using the "grafting from" approach, which rendered the SPIONs soluble in water and reversed aggregation. To the best of our knowledge, this is the first report that describes the functionalization of magnetic nanoparticles with dendritic-linear-brush-like triblock copolymers. The modified nanoparticles were systematically studied via TEM, FT-IR, DLS, XRD, NMR, TGA, and magnetization measurements. DLS measurement confirmed that the obtained dendritic-linear-brush-like triblock copolymer-grafted SPIONs had a uniform hydrodynamic particle size of average diameter less than 30 nm. The dendritic-linear-brush-like triblock copolymer-grafted SPIONs possessed excellent biocompatibility by methyl tetrazolium (MTT) assays against NIH3T3 cells and hemolysis assays with rabbit erythrocytes. Furthermore, an anticancer drug, doxorubicin (Dox), was used as a model drug and loaded into the dendritic-linear-brush-like triblock copolymer-grafted SPIONs, and subsequently, the drug releases were performed in phosphoric acid buffer solution pH = 4.7, 7.4, or 11.0 at 37 °C. The results verify that the dendritic-linear-brush-like triblock copolymer-grafted SPIONs possess pH-responsive drug release behavior. The Dox dose of the loaded and free drug required for 50% cellular growth inhibition was 2.72 and 0.72 μm/mL, respectively, according to MTT assay against a Hella cell line in vitro. Therefore, on the basis of its biocompatibility and drug release effect, the modified SPION could provide a charming opportunity to design some excellent drug delivery systems for therapeutic applications.

Hyperbranched poly(amido amine)s (HPAAs) containing different amounts of β-cyclodextrin (β-CD) (HPAA-CDs) were synthesized in one-pot by Michael addition copolymerization of N,N'-methylene bisacrylamide, 1-(2-aminoethyl)piperazine, and mono-6-deoxy-6-ethylenediamino-β-CD. In comparison to pure HPAA, the fluorescence intensity of HPAA-CDs was enhanced significantly while the cytotoxicity became lower. Ascribed to plenty of amino groups and strong photoluminescence, HPAA-CDs could be used as nonviral gene delivery vectors, and the corresponding gene transfection was evaluated. The experimental results indicated that HPAA-CDs condensed the plasmid DNA very well. By utilizing the fluorescent properties of HPAA-CDs, the cellular uptake and gene transfection processes were tracked by flow cytometry and confocal laser scanning microscopy without any fluorescent labeling. The transfection efficiencies of HPAA-CDs were similar to that of pure HPAA. In addition, the inner cavities of β-CDs in HPAA-CDs could be used to encapsulate drugs through host--guest interaction. Therefore, the HPAA-CDs may have potential application in the combination of gene therapy and chemotherapy.

A general strategy to improve the transfection efficiency as well as lower the cytotoxicity for polycationic vectors has been developed. Through the polycondensation addition of N,N'-methylene bisacrylamide and 1-(2-aminoethyl)piperazine in a water/N,N-dimethylformamide cosolvent, a series of cationic poly(amido amine)s with same repeating units but different branched architecture have been prepared. With the increase in branched architecture, the cationic polymers become more and more compact, accompanied by the enhancement of primary and tertiary amino groups. Therefore, the buffering capacities and DNA condensation capabilities of cationic poly(amido amine)s are strengthened greatly, whereas the correspondent cytotoxicity decreases. Correspondingly, the transfection efficiency is improved by more than three orders of magnitude. The results of this study indicate that the gene delivery can be readily regulated by only changing the branched architecture of polycations.

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSynthesis of Hyperbranched Polyphosphates by Self-Condensing Ring-Opening Polymerization of HEEP without CatalystJinyao Liu, Wei Huang*, Yongfeng Zhou, and Deyue Yan*View Author Information School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, P. R. China*Corresponding authors. E-mail address: (W.H.) [email protected]; (D.Y.) [email protected]Cite this: Macromolecules 2009, 42, 13, 4394–4399Publication Date (Web):June 4, 2009Publication History Received11 April 2009Revised18 May 2009Published online4 June 2009Published inissue 14 July 2009https://doi.org/10.1021/ma900798hCopyright © 2009 American Chemical SocietyRequest reuse permissions Article Views2573Altmetric-Citations77LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (1002 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Anions,Nuclear magnetic resonance spectroscopy,Phosphates,Phosphorus,Polymerization Get e-Alerts

Catalytic performance of Ce–Fe mixed oxides promoted with ZrO2 was investigated for methane partial oxidation to syngas via gas–solid reactions. The results showed that moderate amounts of ZrO2 could strongly enhance the interaction between iron and cerium oxides via increasing the oxygen vacancy concentration and improving the dispersion of free Fe2O3, which improved the activity of Ce–Fe material for methane partial oxidation. However, heavy loading of ZrO2 would lead to a phase segregation of CeO2 and Fe2O3 from the Ce–Fe solid solution, resulting in a decrease in syngas selectivity. Among the tested samples, Ce–Fe–Zr (0.05) sample showed the best catalytic performance (with both high methane conversion and syngas selectivity). Despite severe sintering, the Ce–Fe–Zr (0.05) oxides presented high catalytic stability during the repetitive redox process (methane reduction/air re-oxidation) for the continuous production of syngas. This property should be attributed to the increased oxygen vacancy concentration on the mixed oxides after cycling, which could improve the lattice oxygen mobility, counteracting the native effect of material sintering on the catalytic activity for methane partial oxidation.

A facile supramolecular approach for the preparation of charge-tunable dendritic polycations, by a combination of the multi-functionality of dendritic polymers with the dynamic-tunable ability of supramolecular polymers, has been developed. It provides a new strategy for designing and developing efficient gene vectors via noncovalent interactions.

Dendritic multiarm copolymers, including dendrimer multiarm copolymers and hyperbranched multiarm copolymers, have shown great potential to be excellent precursors in self-assembly, and many impressive supramolecular structures have been prepared through the solution self-assembly of them. However, the corresponding theoretical studies on the self-assembly mechanism have been greatly lagging behind. Herein, we report the micellization behaviors of amphiphilic dendritic multiarm copolymers with a hydrophobic dendritic core and many hydrophilic arms by dissipative particle dynamics simulations. Both the self-assembly mechanisms and the dynamic self-assembly processes for the formation of unimolecular micelles, microphase-separated small micelles, and large multimolecular micelles have been disclosed through the simulations. Most importantly, the work has proved the large multimolecular micelles are a kind of multimicelle aggregate (MMA) with two formation mechanisms. One is called the unimolecular micelle aggregate (UMA) mechanism, which describes the formation of large multimolecular micelles from direct aggregation of unimolecular micelles; the other is called the small micelle aggregate (SMA) mechanism, which shows that the dendritic multiarm copolymers first self-assemble into small micelles and then the small micelles further aggregate into large multimolecular micelles. In addition, the microphase separation model of the dendritic multiarm copolymers as well as the effects on the formations of UMAs and SMAs are also discussed. These simulation results agree well with experimental observations, and have extended the understanding of the micellization process of dendritic multiarm copolymers.

The hydrophobic block of polymeric micelles formed by amphiphilic copolymers has no direct therapeutical effect, and the metabolites of these hydrophobic segments might lead to some unexpected side effects. Here the hydrophobic core of polymeric micelles is replaced by highly water-insoluble drugs themselves, forming a new micellar drug delivery system. By grafting hydrophobic drugs of paclitaxel (PTX) onto the surface of hydrophilic hyperbranched poly(ether-ester) (HPEE), we constructed an amphiphilic copolymer (HPEE-PTX). HPEE-PTX could self-assemble into micellar nanoparticles in aqueous solution with tunable drug contents from 4.1 to 10.7%. Moreover, the hydrolysis of HPEE-PTX in serum resulted in the cumulative release of PTX. In vivo evaluation indicated that the dosage toleration of PTX in mice had been improved greatly and HPEE-PTX micellar nanoparticles could be used as an efficient prodrug with satisfactory therapeutical effect. We believe that most of the lipophilic drugs could improve their characters through this strategy.

Chemotherapy is one of the major systemic treatments for cancer, in which the drug release kinetics is a key factor for drug delivery. In the present work, a versatile fluorescence-based real-time monitoring system for intracellular drug release has been developed. First, two kinds of star-conjugated copolymers with different connections (e.g., pH-responsive acylhydrazone and stable ether) between a hyperbranched conjugated polymer (HCP) core and many linear poly(ethylene glycol) (PEG) arms were synthesized. Owing to the amphiphilic three-dimensional architecture, the star-conjugated copolymers could self-assemble into multimicelle aggregates from unimolecular micelles with excellent emission performance in the aqueous medium. When doxorubicin (DOX) as a model drug was encapsulated into copolymer micelles, the emission of star-conjugated copolymer and DOX was quenched. In vitro biological studies revealed that fluorescent intensities of both star-conjugated copolymer and DOX were activated when the drug was released from copolymeric micelles, resulting in the enhanced cellular proliferation inhibition against cancer cells. Importantly, pH-responsive feature of the star-conjugated copolymer with acylhydrazone linkage exhibited accelerated DOX release at a mildly acidic environment, because of the fast breakage of acylhydrazone in endosome or lysosome of tumor cells. Such fluorescent star-conjugated copolymers may open up new perspectives to real-time study of drug release kinetics of polymeric drug delivery systems for cancer therapy.

A novel class of azobenzene-containing polymeric systems with reversible trans–cis photoisomerization behavior driven by visible light (ca. 450 nm) has been successfully prepared and this opens up a pathway for azobenzene-based systems in biomedical applications.

Abstract In this study, we report a mild and efficient strategy for growing thermosensitive polymers directly from the surface of exfoliated graphene oxide (GO). Exfoliated GO sheets were sequentially subject to the epoxide ring‐opening reaction with tris(hydroxymethyl) aminomethane (TRIS) to increase the amount of reactive sites, the esterification with 2‐bromo‐2‐methylpropionyl bromide to introduce the Br‐containing initiating groups, and the surface‐initiated single electron transfer–living radical polymerization of N ‐isopropylacrylamide (NIPAM) to tune the molecular weights of grafted polymers. All these reactions were performed at ambient temperature without losing any other oxygen‐containing functionality on GO. The resulting TRIS‐GO‐PNIPAM nanocomposites still maintain the separated single layers in dispersion, and the dispersibilities in organic solvents are significantly improved. Meanwhile, the aqueous dispersion of TRIS‐GO‐PNIPAM shows reversible temperature switching self‐assembly and disassembly behavior at about 40°C. Such smart graphene‐based hybrid materials are promising for applications in nanoelectronics, sensors, and microfluidic switches. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012