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

For a series of copolymers of aromatic para- and meta-1,3,4-oxadiazoles with a variable content of the components, the flow birefringence (the Maxwell effect) and orientation of macromolecules in sulfuric acid solutions were studied. Based on hydrodynamic data, the molecular masses of the copolymers and the related homopolymers lie in the range (25-33) x 10(3), which corresponds to the number of segments in a molecular chain ranging from 19 to 21. Comparison of the dynamooptical data obtained for the copolymers and homopolymers indicates that the dependence of flow birefringence on the molar composition of the copolymer follows the additivity law of the chain flexibility mechanisms.