Influence of structural and topological constraints on the crystallizationand melting behavior of polymers: 3. Bisphenol A polycarbonate

In this paper, we report differential scanning calorimetry studies of the t emperature and molar mass dependences for the primary and secondary crystal lization behavior of bisphenol A polycarbonate (BAPC). The molar mass depen dence of the crystallization rate is found to be much stronger during prima ry than during secondary crystallization, confirming our earlier claims tha t primary and secondary processes occur by significantly different mechanis ms. Investigations of the secondary crystallization process suggest the exi stence of a crossover phenomenon from secondary crystal formation at low te mperatures to isothermal lamellar thickening at high temperatures. While th e results of our low-temperature studies of BAPC provide further support fo r the model developed in a previous publication on poly(arylene ether ether ketone), evidences from atomic force microscopy and calorimetry of isother mal lamellar thickening above the crossover temperature lead us to anticipa te a more unified view of polymer crystallization.