Polycarbonate, conventional synthesis

In an attempt to identify new, biocompatible diphenols for the synthesis of polyiminocarbonates and polycarbonates, we considered derivatives of tyrosine dipeptide as potential monomers. Our experimental rationale was based on the assumption that a diphenol derived from natural amino acids may be less toxic than many of the industrial diphenols. After protection of the amino and carboxylic acid groups, we expected the dipeptide to be chemically equivalent to conventional diphenols. In preliminary studies (14) this hypothesis was confirmed by the successful preparation of poly(Z-Tyr-Tyr-Et iminocarbonate) from the protected tyrosine dipeptide Z-Tyr-Tyr-Et (Figure 3). Unfortunately, poly (Z-Tyr-Tyr-Et iminocarbonate) was an insoluble, nonprocessible material for which no practical applications could be identified. This result illustrated the difficulty of balancing the requirement for biocompatibility with the need to obtain a material with suitable "engineering" properties. 

Bisphenol-A (BPA) is an important raw material for the synthesis of polycarbonates, epoxy resins and other polymers as well as polymer additives. It is conventionally produced by acid-catalysed condensation of phenol with acetone. Application of various catalysts for the BPA synthesis is discussed with particular attention to the substrates conversion and the reaction selectivity. Recent developments in the BPA production and its applications are presented. Moreover, potential toxicological and endocrine disrupting properties of BPA are considered with the emphasis on human exposure, general toxicology, and biological effects. 

The use of solid-liquid phase transfer catalysis in the conjunction with bis(carbonylimidazolides) (i) bis(p-nitrophenylcarbonates) 10) as developed by Fre-chet for the synthesis of novel tertiary copolycarbonates. The instability of tertiary chloroformates renders tertiary polycarbonates inaccessible through conventional chloroformate monomers or intermediates. The bis(carbonylmiidazoiide) monomer was shown to polymerize with both tertiary (3) and secondary alcohols (lljy demonstrating the utility of the method in forming polycarbonates fi-om less reactive steri-cally hindered monomers. Most of the examples reported involved benzene dimethanol derivatives, or 1,4-butynediol, indicating that an adjacent site of unsaturation may activate the alcohol in the solid-liquid phase transfer reaction scheme. 

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