Flow birefringence and optical anisotropy of molecules of copolymers of para- and meta-phenylene-1,3,4-oxadiazoles

Flow birefringence (Maxwell effect) and orientation of macromolecules were investigated in a flow of sulphuric acid solutions of some copolymers of me ta- and para- aromatic 1,3,4-oxadiazoles differing in the molar content of the components. According to hydrodynamic data, the molecular weights of sa mples of copolymers and the corresponding homopolymers range from M = 25 x 10(3) to 33 x 10(3). This corresponds to the number of segments in the chai n from 19 to 21. Comparison of dynamo-optical data with the corresponding p roperties of homopolymers has shown that the dependence of flow birefringen ce on the molar composition of the copolymer obeys the additivity law of ch ain flexibilities. (C) 2000 Elsevier Science Ltd. All rights reserved.