Synthesis of poly(N-(2-hydroxypropyl) methacrylamide) brushes by interface-mediated RAFT polymerization

Abstract

The synthesis of poly(N-(2-hydroxypropyl) methacrylamide) [poly(HPMA)] brushes is reported using an interface-mediated reversible addition–fragmentation chain transfer (RAFT) polymerization on a silicon substrate. To produce a RAFT agent immobilized surface, 4-cyano-4-(propylsulfanylthiocarbonyl)sulfanyl pentanoic acid was reacted with 9-decen-1-ol to form a self-assembled monolayer. Poly(HPMA) brushes and free polymers of varied molecular weights between 10 100 and 48 500 g mol⁻¹ were then synthesized by RAFT polymerization. The chemical characterization of the modified surfaces was examined using atomic force microscopy, grazing angle-Fourier transform infrared and X-ray photoelectron spectroscopy, ellipsometry and water contact angle measurements. The average distance between grafting sites (D, nm) and grafting density (σ, chains per nm²) of poly(HPMA) brushes calculated from the dry film thickness (h, nm) and the number-average molecular weight (_n) of the free polymers were 1.3 nm and 0.52 chains per nm², respectively, indicating moderate density polymer brush formation.