Microheterophase structure, permeability, and biocompatibility of A-B-A triblock copolymer membranes composed of poly(gamma-ethyl L-glutamate) as the A component and polybutadiene as the B component.

A-B-A block copolymers (EBE) consisting of poly(gamma-ethyl L-glutamate) as the A component and polybutadiene as the B component were synthesized. The microheterophase structure of these block copolymers, as observed microscopically, was less distinct than that of the block copolymer (GBG) composed of poly(gamma-benzyl L-glutamate) as the A component. This was attributed to the better compatibility of the ethyl group with polybutadiene block, compared with the benzyl group. The observed micelle size of various microheterophase structures ranged from 350 to 480 A, which agreed well with the micelle size estimated from a thermodynamic study. From the measurement of water permeation through the EBE block copolymer membranes, the contributions of the interfacial region between the alpha-helical polypeptide domain and polybutadiene domain to the permeability coefficient were concluded to be higher than those of poly(gamma-methyl L-glutamate)-polybutadiene block copolymer (MBM) membranes, i.e., more hydrophilic domain seemed to exist in EBE membranes than in MBM membranes. The results of in vivo tests on the tissue compatibility indicate that the EBE block copolymer membranes have good biocompatibility.