Selective growth of thermo-responsive polymer brushes through orthogonal self-assembly
Giasuddin, Abul Bashar Mohammad
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In this work, thermally responsive poly(N-isopropyl acrylamide) or p(NIPAM) brushes were successfully grafted to multi-component surfaces with chemical selectivity. A catechol based photo-initiator was synthesized and selectively assembled on the surface prior to polymerization. Orthogonal formation of both monolayers and surface selective polymer brushes were confirmed by FTIR. Thick and homogeneous growth of pNIPAM polymer brushes selectively on TiO2 surfaces with dual SiO2-TiO2, was observed using SEM and optical microscopy. Controlled growth of pNIPAM brushes was possible using both different monomer concentrations and photo-irradiation time. Thickest brushes were achieved at saturation concentration of monomer (87% w/w) in solvent and a linear growth in polymer brush thickness formation was observed up to 20 hours of irradiation. The thermal responsive behavior of pNIPAM brushes was confirmed using static contact angle below and above the LCST (Lower Critical Solution Temperature) of pNIPAM. Swelling studies were also performed to estimate the water uptake and release from brush layers below and above LCST.