Multiple transitions in polycarbonate

Two kinds of dielectric absorptions due to motion of carbonate groups in polycarbonate were observed. In the primary transition region near 150°C, the shape of e′ versus log frequency curve is little affected by a temperature change, while it becomes more widely spread when the polymer is partially crystallized. In contrast, in the secondary transition region near −120°C., the shape of e′ versus log frequency curve is greatly affected by a temperature change, but it is not sensitive to the crystallinity. By using a conclusion drawn from a separate study that an increase in width of the loss curve is a manifestation of segments that are constrained, it is suggested here that the secondary transition involves local motions which persist in a highly restricted framework of glassy polymer chains and that such restriction becomes more pronounced at lower temperatures. Results from the PVT and x‐ray studies are consistent with the above concept, i.e., glassy polymers in general contain enough space so that limited local motions arc allowed that give rise to the low temperature transition.