Synthesis and characterization of poly(N-[3-(dimethylamino)propyl]methacrylamide) brushes covalently attached to silicon disc by surface-initiated reversible addition-fragmentation chain transfer polymerization

In this study, stimuli-responsive poly(N-[3-(dimethylamino)propyl] methacrylamide) (PDMAPMA) brushes covalently attached to Si(100) wafer surface were prepared by surface-initiated reversible addition-fragmentation chain transfer (RAFT) technique. Firstly, RAFT agent, 4- cyanopentanoic acid dithiobenzoate (CPAD) was synthesized and immobilized on the silicon wafer surface via covalent attachment of the R-group. RAFT polymerization of DMAPMA was conducted on the silicon wafer surface. The resulting polymer brushes were characterized by ellipsometry, X-ray photoelectron spectra (XPS), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM) and contact angle measurements. Chemical composition of the brushes on the silicon surfaces was determined by X-ray photoelectron spectroscopy (XPS). The C1s, N 1s and S 1s peaks in the XPS spectrum can qualitatively account for the existence of 3-aminopropyltriethoxysilane (APTES), CPAD and PDMAPMA molecules on the silicon surface. The ATR-FTIR analysis of the PDMAPMA indicated that the DMAPMA have been `?grafted from?? the modified silicon surface. AFM analysis showed that the surface initiated polymerization via RAFT had proceeded uniformly on the RAFT agent-immobilized silicon wafer surface. Kinetic studies revealed a linear increase in thickness of the surface graft-polymerized film with reaction time. It indicated that the chain growth from the surface was a controlled process with a `?living?? character.