Covalently tethered comb-like polymer brushes on hydrogen-terminated Si (100) surface via consecutive aqueous atom transfer radical polymerization of methacrylates

摘要

The hydrogen-terminated Si (100) (Si-H surface) was functionalized by coupling with 4-vinylbenzyl chloride (VBC) to form a Si-VBC surface, which serves as macro-initiators for the surface-initiated aqueous atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)methacrylate (PEGMA) to prepare Si-VBC-g-PHEMA and Si-VBC-g-PPEGMA substrates, respectively. The ellipsometric results revealed that the surface-initiated ATRP of both PHEMA and PPEGMA brushes proceeded in a controlled fashion. By adjusting the monomer concentration, an eccentric polymer thickness dependence on the initial monomer concentration [M](0) was observed for both HEMA and PEGMA, i.e., in the dilute regime, the thickness of the polymer film increases with the increase in [M](0); however, beyond critical [M](0), the thickness deceases gradually with the further increase. Such an eccentricity was tentatively correlated to the counteractive combination of the increase in [M](0) and decrease in the apparent polymerization rate constant. Both Si-VBC-g-PHEMA and Si-VBC-g-PPEGMA substrates were esterified for the subsequent surface-initiated ATRP, resulting in corresponding comb-like brushes. (c) 2006 Wiley Periodicals, Inc.