Preparation of copoly(carbonate/urethanes) from polycarbonates

When solutions of high molecular weight poly(diphenylolpropane carbonate) were treated with aliphatic primary and secondary diamines in a homogeneous system, degradation to hydroxyl‐terminated copoly(carbonate/urethane) macrosegments occurred. This observation led to a novel method for the preparation of high molecular weight copoly(carbonate/urethanes). This involved (1) preparation of high molecular weight polycarbonate, (2) degradation of the polycarbonate to a low molecular weight urethane‐bisphenol, (3) repolymerization with phosgene. The composition of the final copolymer could be regulated by the amount of diamine empolyed in step (2). High molecular weight copolymers were thus prepared from poly(diphenylolpropane carbonate) and piperazine, ethylene diamine, hexamethylene diamine, p‐xylylene diamine and hydrazine. These copolymers could be converted to tough drawable films which showed greatly improved hydrolytic stability over unmodified poly(diphenylolpropane carbonate).