STRAIN-INDUCED BIREFRINGENCE AND MOLECULAR-STRUCTURE OF GLASSY-POLYMERS

The dynamic birefringence and viscoelasticity were measured for poly(e thylene naphthalene-2,6-dicarboxylate), and the contributions from the main chain orientation and the rotational orientation of repeating un it to the strain-induced birefringence were evaluated. The values, tog ether with published ones for other glassy polymers, were compared wit h the anisotropy of polarizability tensor of the repeating units. The contribution from the main chain orientation for various polymers was in accord with that evaluated from the excess polarizability of the un it in the main chain direction assuming a quasi-affine orientation of the unit. The contribution from the rotation was well correlated with the anistropy in the plane perpendicular to the chain axis. The degree of the rotational orientation was similar among the polymers. The rot ational orientation was high for vinyl polymers with large side-groups . (C) 1997 Elsevier Science Ltd.