Versatility of a succinimidyl-ester functional alkoxyamine for controlling acrylonitrile copolymerizations

摘要

Styrene/acrylonitrile (S/AN) and tert-butyl methacrylate/acrylonitrile (tBMA/AN) copolymers were synthesized in a controlled manner (low polydispersity M_w/M_n with linear growth of number average molecular weight M_n vs. conversion X) by nitroxide mediated polymerization (NMP) with a succinimidyl ester (NHS) terminated form of BlocBuilder unimolecular initiator (NHS-BlocBuilder) in dioxane solution. No additional free nitroxide (SG1) was required to control the tBMA-rich copolymerizations with NHS-BlocBuilder, a feature previously required for methacrylate polymerizations with BlocBuilder initiators. Copolymers from S/AN mixtures (AN molar initial fractions f_(AN,0) = 0.13-0.86, T = 115°C) had M_w/M_ n = 1.14-1.26 and linear M_n versus conversion X up to X ≈ 0.6. tBMA/AN copolymers (f_(AN,0) = 0.10-0.81, T = 90°C) possessed slightly broader molecular weight distributions (M_w/M _n = 1.23-1.50), particularly as the initial composition became richer in tBMA, but still exhibited linear plots of M_n versus conversion X up to X ≈ 0.6. A S/AN/tBMA terpolymerization (f_(AN,0) = 0.50, f_(S,0) = 0.40) was also conducted at 90°C and revealed excellent control with M_n = 13.6 kg/mol, Mw/Mn = 1.19, and linear Mn versus conversion X up to X = 0.54. Incorporation of AN and tBMA in the final copolymer (molar composition F_(AN) = 0.47, F_(tBMA) = 0.11) was similar to the initial composition and represents initial designs to make tailored, acid functional AN copolymers by NMP for barrier materials.