INTERCHAIN PACKING IN BISPHENOL-A POLYCARBONATE

Bisphenol A polycarbonates prepared with varying thermal history have been examined by dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR). The results are consistent with a description of interchain packing in polycarbonate based on local regions of aligned chains referred to as bundles. In this model, two distinct types of cooperative, interchain motions are possible: those of chains within one bundle and those of one bundle relative to another. We believe that low-frequency DMS (tan delta at 0.01 Hz) and stress-relaxation DMS (at 10 s) identify a loss peak at -120 degrees C arising from intrabundle motion and another at -80 degrees C due to interbundle motion. Results from DMS, DSC, and dipolar rotational spin-echo C-13 NMR suggest that acetone-induced crystallization suppresses intrabundle motions, while residual acetone enhances interbundle motions. Interpretation of residual-proton NMR of perdeuterated polycarbonate leads to the conclusion that interbundle motions are sensitive to thermal history and that annealing at T < T-g reduces interbundle spacing.