Substituent Effects in the Surface-Initiated ATRP of Substituted Styrenes

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 surface. 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 ρ = 0.51. The ratio of k_p to k_t, is as an indicator of the likelihood that a reaction will reach high degrees of polymerization before termination.

Photoactivatable glycopolymers for the proteome-wide identification of fucose-α(1-2)-galactose binding proteins

Although fucose-α(1-2)-galactose (Fucα(1-2)Gal)-containing glycans have been implicated in cognitive processes such as learning and memory, their precise molecular mechanisms are poorly understood. Here we employed the use of multivalent glycopolymers to enable the first proteome-wide identification of weak affinity, low abundance Fucα(1-2)Gal glycan-binding proteins (GBPs). Biotin-terminated glycopolymers containing photoactivatable cross-linking groups were designed to capture and enrich GBPs from rat brain lysates. Candidate proteins were tested for their ability to bind Fucα(1-2)Gal, and the functional significance of the interaction was investigated for the synaptic vesicle protein SV2a using a knockout mouse system. The results suggest a role for SV2a-Fucα(1-2)Gal interactions in SV2a trafficking and synaptic vesicle recycling. More broadly, our studies outline a general chemical approach for the systems-level discovery of novel GBPs.

Rapid Growth of Polymer Brushes from Immobilized Initiators

This report describes the remarkably rapid synthesis of polymer brushes under mild conditions (50 degrees C) using surface-initiated polymerization. The highly active atom transfer radical polymerization catalyst Cu(I)-1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane allows synthesis of 100 nm thick poly(tert-butyl acrylate) brushes from initiator-modified Au surfaces in just 5 min. Using the same catalyst, polymerization of 2-hydroxyethyl methacrylate and methyl methacrylate yielded 100 nm thick films in 10 and 60 min, respectively. Such growth rates are an order of magnitude greater than those for traditional free-radical polymerizations initiated from surfaces. These polymerizations also retain some features of controlled radical polymerizations, such as the ability to form block copolymer brushes.