HYDROSTATIC-PRESSURE DEPENDENCE OF MOLECULAR MOTIONS IN POLYCARBONATES

The temperature dependence of the proton NMR line width of polycarbonate and of the phenoxy resin formed from bisphenol A and epichlorohydrin have been measured as a function of hydrostatic pressure. These measurements lead to the conclusion that for both polymers, ring motions are suppressed by the denser chain packing resulting from hydrostatic pressure. The magnitude of the NMR pressure dependence is comparable to the pressure variation of the γ mechanical loss peak in polycarbonate. The1H NMR results, together with those from a variety of cross-polarization magic-angle spinning13C NMR experiments performed at room temperature and atmospheric pressure, are interpreted in terms of a bundle model of chain packing in the glassy matrix. From the observed activation volumes, activation energies, and main-chain reorientation rates, the bundles are inferred to involve the correlated motions of just a few chains. © 1990, American Chemical Society. All rights reserved.