Comparison of polycarbonate precursors synthesized from catalytic reactions of bisphenol-A with diphenyl carbonate, dimethyl carbonate, or carbon monoxide

Transesterification of bisphenol-A with diphenyl carbonate or dimethyl carbonate, and direct oxidative carbonylation of bisphenol-A were compared to obtain polycarbonate precursors for phosgene-free polycarbonate synthesis. The melt-transesterification of bisphenol-A and diphenyl carbonate occurred readily to produce reactive precursors without a significant equilibrium constraint. On the other hand, the transesterification of bisphenol-A and dimethyl carbonate showed a serious equilibrium limitation in obtaining reactive polycarbonate precursors leading to high molecular weight polymers, and coproduced a significant amount of methylated bisphenol-A. The direct oxidative carbonylation of bisphenol-A with CO produced diphenolic-ended oligomers and a significant amount of by-products, which are the least reactive in the subsequent polycondensation step of the phosgene-free polycarbonate process. A novel method to synthesize the reactive polycarbonate precursors was proposed that employed the coupled oxidative carbonylation of both bisphenol-A and phenol. (C) 2002 Wiley Periodicals, Inc.