APPROXIMATION OF THE CHAIN MODULUS OF AROMATIC POLYESTERS AND A POLY-PARA-PHENYLENE WITH ALIPHATIC SIDE-CHAINS

A systematic series of well-defined aromatic polyesters and a poly-par a-phenylene with aliphatic side chains were investigated. Films were m echanically characterized by DMTA. The chain modulus was estimated usi ng an extrapolation method based on the aggregate model. The extrapola ted values are comparable with theoretically calculated moduli, but di splay a fairly large uncertainty. Comparison of the theoretical values with the experimentally attained moduli showed an increasing discrepa ncy for higher molecular rigidity. The theoretical modulus increases w ith increasing molecular rigidity, while the experimental moduli (at l ow temperature and corrected for the cross-sectional area of the side chains) do not exhibit a specific dependence on the molecular rigidity , and range between 140 and 180 GPa. This important effect was ascribe d to increasing processing difficulties, which is shown by the maximum draw ratio obtained. (C) 1998 Elsevier Science Ltd. All rights reserv ed.