ABSTRACT
A. Introduction and Early Studies It has long been thought likely that the exceptional ductility of bisphenol A polycarbonate (BPA-PC) (Fig. 1) is in some way linked to specific intramolecular motions of the polymer chain. Direct evidence for rapid and extensive solid state motion in glassy polycarbonate is seen in the large, low-temperature, dynamic mechanical loss peak found at -100°C at I Hz [1,2]. This glassy state loss peak is frequently called the yprocess (e.g. [3]) since between it and the higher temperature glass transition at Tg (i.e., the a process) is found a smaller intensity f3 process at a temperature T~ whose magnitude and position are sensitive to the thermal and mechanical history of the sample. The temperature Ty of the loss peak maximum and the intensity of the y process, on the other hand, are quite insensitive to thermal and mechanical history. Furthermore, the unperturbed chain dimensions ofBPA-PC in solution are independent of temperature [4], suggesting
0 7 II o-c-o Figure 1 Molecular structure of bisphenol A polycarbonate (BPA-PC).
