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 meta- and para- aromatic 1,3,4-oxadiazoles differing in the molar content of the components. According to hydrodynamic data, the molecular weights of samples of copolymers and the corresponding homopolymers range from M=25×103 to 33×103. This corresponds to the number of segments in the chain from 19 to 21. Comparison of dynamo-optical data with the corresponding properties of homopolymers has shown that the dependence of flow birefringence on the molar composition of the copolymer obeys the additivity law of chain flexibilities.