Local Conformations in the Glassy Polycarbonate of 2,2-Bis(4-hydroxyphenyl)propane (Bisphenol-A)

NMR experiments were carried out on glassy samples containing 13 C-labeled bisphenol-A polycarbonate with isolated C* carbonate −O−C* phenylene arrangements in the chains. The dihedral angle distributions in the C−O−C moieties were determined by fitting simulated spectra to the experimental data. It was found that the O−C phenylene torsion angle is widely distributed with population maxima where the C−O−C plane forms an angle of ca. 55° with the phenylene ring. The carbonate units assume trans conformations at 135 K (torsion angle around C* carbonate −O < 10% cis ). Three different molecular packings obtained by computer simulation with different construction methods and two different force fields yielded considerably higher cis contents; this discrepancy is currently still unresolved. From comparison of the data to those for single-chain models (rotational-isomeric-state models) it is concluded that considerable conformational change could be possible far below T g .