Surface Modification of Polyvinyl Chloride Sheets via Growth of Hydrophilic Polymer Brushes

Poly(N,N-dimethylacrylamide) (PDMA) brushes were successfully grown from polyvinyl chloride (uPVC) sheets via well-controlled surface-initiated atom transfer radical polymerization (SI−ATRP). An ATRP initiator containing a chloropropionate moiety was chemically tethered onto the surface of PVC via a novel wet chemical modification. Negatively charged sulfate groups were introduced to facilitate polymerization. By incorporating a chemically cleavable group into the initiator, molecular weight, polydispersity and graft density of a series of PDMA brushes synthesized on the flat surface were unambiguously characterized for the first time by gel permeation chromatography. ATR−FTIR, contact angle, SEM and AFM were used to characterize the PDMA grafted surfaces. Reaction conditions such as monomer concentration, reaction time, copper(II) concentration and salt additives were varied to systematically investigate their effects on molecular weight and graft density of the PDMA grafted from PVC. Molecular weights of grafted PDMA brushes varied from ca. 20 000 to 2 170 000 Da, while graft density ranged from 0.08 to 1.13 chains/nm2. Polydispersity of grafted PDMA brushes was controlled between 1.20 and 1.60 by Cu(II) complex addition. Kinetic studies revealed that the surface initiation was a slow process and graft density increased during the reaction. The brush uniformity increased with increasing reaction time. Reinitiation of the obtained PDMA brushes was demonstrated, suggesting that the polymerization is "living". The successful growth of a PDMA-b-poly(N-isopropylacrylamide) (PNIPAM) copolymer brush was verified by GPC and AFM.