Nitroxide Mediated Synthesis of Protected Styrenesulfonate and Acrylonitrile Copolymers for Membrane and Barrier Materials.

摘要

Controlled free radical polymerization is attractive as it produces polymers with well defined microstructures typically associated with "living" polymerization methods, using a wide range of monomers required for applications such as nanoporous membranes and barrier materials. Poly(trioctylammonium p-styrenesulfonate) homopolymer (poly(SS-TOA)) and poly(SS-TOA-ran-styrene) copolymers were synthesized by nitroxide-mediated polymerization (NMP) using an N-tert-butyl-N-[1-diethylphosphono-(2,2-dimethylpropyl)] nitroxide (SG1) based unimolecular initiator, called BlocBuilder. Polymerizations were controlled for low theoretical molecular weight at complete conversion (Mn,theoretical = 20 kg˙mol-1 ), resulting in very low polydispersities (M w/Mn < 1.1) and a linear increase in number average molecular weight, Mn, up to ≈ 35% conversion. SS-TOA was effective as a controlling co-monomer for the gradient polymerization with glycidyl methacrylate, using a N-succinimidyl ester modified BlocBuilder (NHS-BlocBuilder), which resulted in a relatively narrow molecular weight distribution (Mw/ Mn = 1.43) and linear increase in M n versus conversion. Poly(styrene-ran-acrylonitrile) (poly(S/AN)) and poly(tert-butyl methacrylate-ran -acrylonitrile) (poly(t-BMA/AN)) were also synthesized by NMP using BlocBuilder and NHS-BlocBuilder. In both systems, the polymers exhibited narrow, monomodal molecular weight distributions with relatively low polydispersities (Mw/M n = 1.14-1.50), characteristic of a controlled polymerization. Mn versus conversion (X) plots were all relatively linear (Mn = 14.8-18.1 kg.mol-1, X = 40-70%) suggesting that "pseudo-living" behaviour was approached in the range of conversions studied.