| Surface initiated atom transfer radical polymerization (ATRP) of substituted styrenes leads to rapid synthesis of uniform and thick substituted polystyrene brushes (>100 nm in 1 hour) from gold and silicon surfaces. High growth rates were observed for styrenes substituted with electron withdrawing groups in meta/para positions. The effects seen in surface and solution polymerizations are similar for styrenes with electron withdrawing groups, and for electron donors in ortho and para positions. However, electron donors at meta sites have surprisingly fast growth rates, which may be due to steric inhibition of termination. The overall surface polymerization rates for substituted styrenes was analyzed and found to follow the Hammett relation with rho = 0.51. The ratio of kp to kt, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.;During surface initiated polymerization, thiols desorb from gold surfaces at low temperatures (< 60 °C) and terminate growing polymers during surface initiated ATRP. Thiol desorption was prevented by forming a cross-linked poly(siloxane) primer layer on the gold surfaces prior to attaching the initiator layer. These modified surfaces provide polymer film thicknesses comparable to films grown from silicon surfaces. This strategy above 100 °C since the film delaminates from the substrate. Usually, difficult monomers, such as 2-vinyl pyridine, a polyelectrolyte precursor, cannot be grown from thio-initiators anchored on gold, but the cross-linked initiator enabled growth of thick polymer films.;Polyacrylate brushes with pendent terthiophenes (PTTMM) were successfully grown from ITO and gold using surface initiated ATRP. Using cyclic voltammetry, the PTTMM brush was electrochemically cross-linked to form a conjugated polymer network. The conjugation lengths in the film were short, but were increased via heterocoupling. These uniformly grafted conducting polymer brushes may find use in photovoltaic devices.;Click chemistry was used for the post-functionalization of hydrophilic polymer brushes. The polymer brushes were random copolymers of AZPMA (azidopropyl methacrylate), a functional monomer with a pendent azo group, and oligo ethylene glycol methyl ether methacrylate (PEGMA) with varying ethylene oxide chain lengths, which enabled control over the hydrophilicity and functional group density in the copolymer. Subsequent post-functionalization of homo and copolymer brushes was demonstrated by appending an alkyne-modified dye to AZPMA via click reactions. Kinetic studies showed that the modification of surface-grafted homo/copolymer brushes was fast (> 60% conversion in 1 min) irrespective of the copolymer composition. In the case of water soluble high molecular weight alkynes, surface-grafted copolymers with highest amount of hydrophilic monomer (PEGMA) gave the highest degree of immobilization, which indicates its potential application in bioconjugation. |
