Synthesis of Cationic N-[3-(Dimethylamino)propyl]methacrylamide Brushes on Silicon Wafer via Surface-Initiated RAFT Polymerization

Abstract

Surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of N-[3-(dimethylamino)propyl]methacrylamide (DMAPMA) on the silicon wafer was conducted in attempt to create controllable cationic polymer films. The RAFT agent-immobilized substrate was prepared by the silanization of hydroxyl groups on silicon wafer with 3-aminopropylthriethoxysilane (APTS) and by the amide reaction of amine groups of APTS with ester groups of 4-cyano-4-((thiobenzoyl) sulfanyl) pentanoic succinimide ester (CPSE); followed by the RAFT polymerization of DMAPMA using a "free" RAFT agent, that is, 4-cyanopentanoic acid dithiobenzoate (CPAD) and an initiator, that is, 4,4'-azobis-4-cyanopentanoic acid (CPA). The formation of homogeneous tethered poly(N-[3-(dimethylamino)propyl]methacrylamide) [poly(DMAPMA)] brushes, whose thickness can be tuned by reaction time varying, is evidenced by using the combination of grazing angle attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and water contact-angle measurements. The calculation of grafting parameters from the number-average molecular weight, (M) over bar (n) (g/mol) and ellipsometric thickness, h (nm) values indicated the synthesis of densely grafted poly(DMAPMA) films and allowed us to predict a polymerization time for forming a "brush-like" conformation for the chains. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 423-431, 2011