Synthesis and Gas Permeability of Block Copolymers Composed of Poly(styrene-co-acrylonitrile) and Polystyrene Blocks

Radical copolymerization of a mixture of styrene (S) and acrylonitrile (AN) at azeotropic composition (63 mole % of S and 37 mole % of AN) at 125 °C in the presence of dibenzoyl peroxide and 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) gave TEMPO-terminated S-AN copolymers with narrow molecular weight distributions. Both the linear semilogarithmic time-conversion and molecular weight-conversion dependences indicated a quasiliving copolymerization process. Polymerization of styrene initiated with the synthesized macroinitiators containing reversibly bound terminal TEMPO groups yielded film-forming poly(styrene- co -acrylonitrile)- block -polystyrene copolymers. Using the resulting diblock copolymer as a macroinitiator in copolymerization of S and AN, a triblock copolymer of the A-B-A type was obtained. Films of the block copolymers were prepared by casting chloroform solutions and their permeabilities ( P ) to nitrogen, oxygen, methane, carbon dioxide, and hydrogen were determined. The films showed high selectivities to oxygen ( P O2 / P N2 > 6). The block copolymers behaved as single-phase homogeneous materials.