Bundle description of packing and dynamics in polycarbonate homopolymers, copolymers, and blends

Dipolar-rotational spin-echo C-13 NMR spectra at 15.1 MHz have been obtained for 12 homopolymers, copolymers, and blends of polycarbonate, poly(ether carbonate), poly(ether sulfone), dimethyl polycarbonate, and tetramethyl polycarbonate. The spectra were used to determine the fraction of nonmethylated phenylene rings that are blocked from undergoing pi flips faster than 10 kHz at 300 K. This fraction is interpreted in terms of a simple two-chain bundle packing model in which empirically determined steric parameters specify the interchain interactions between flexible chain linkers and rigid chain extenders. The success of this bundle description suggests that the glassy state for all of these polycarbonate-like systems has local mainchain orientational order.