Chemical modification of bisphenol a polycarbonate by reactive blending with ethylene carbonate

A new method for the insertion of aliphatic moieties into bisphenol A (BPA) polycarbonate (PC) by reactive blending with ethylene carbonate (ETC) has been developed. By this route, new polymeric materials with modified thermal and rheological properties have been synthesized; the structure of the poly(ether-co-carbonate)s prepared can be controlled using different ETC/PC molar ratios. Using model compounds and selective degradation reactions, the different chemical structures of the aliphatic units inserted into PC backbone were identified. ETC/PC molar ratios below 1 afforded both aliphatic-aromatic carbonate and ether groups, while higher ETC/PC molar ratios afforded aliphatic-aromatic ether and aliphatic-aliphatic carbonate groups. The co-polymers prepared by the new process were clear without discoloration or opacity. The thermal analyses of the co-polymers showed that, by the insertion of aliphatic moieties, it is possible to modulate the glass transition temperature (Tg) in a 30°C range. A decreased melt viscosity of the co-polymers was also observed and therefore an improved processability should be expected with respect to standard PC. The reaction with aliphatic carbonates can be also considered as a promising chemical recycling process for PC scraps, through the synthesis of monomers such as bis(hydroxyethyl)ether of BPA. This monomer has already been used for the preparation of co-polyesters of terephthalic acid with high Tg and thermal stability.