CONFORMATIONAL-ANALYSIS OF HIGHLY EXTENDED POLY(ETHYLENE-TEREPHTHALATE) CHAINS BY MONTE-CARLO CALCULATIONS

The conformational disorder compatible with the highly extended chains found in mesomorphic poly(ethylene terephthalate) has been studied by Monte Carlo calculations on model oligomers confined inside cylindrical tubes. The distribution of torsional angles for such extended chains is characterized by O-C-C-O bonds being always in the trans domain, while the C-O-C-C bonds show an approximately similar probability of being found in trans and gauche states, the probability maxima being centered at 90 degrees and -90 degrees in the latter cases. At variance with the torsional angles of the O-C-C-O and the ester bonds, always very close to 180 degrees, the distributions for all other torsional angles show flat and broad probability maxima, indicating the possibility of substantial deviations from the average value inside each domain. This is also true for the fictitious O-(CC)-C-...-O bonds across the phenylene rings, for which a nearly trans geometry is preferred in extended conformations.