Conformational properties of poly-p-phenylene-1,3,4-oxadiazole molecules in sulphuric acid

Abstract

Hydrodynamic and dynamo-optical properties of samples of poly- p-phenylene-1,3,4-oxadiazole (POD) with molecular weights from 4.6 × 10 3 to 100 × 10 3 in dilute solution in 96 and 100% sulphuric acid have been investigated. Molecular-weight dependence of intrinsic viscosity for POD in 96% H 2SO 4 was established by light scattering and viscometry methods as [η] 96= M ̄ w 2(52 + 0.77 × M ̄ w 1 2 ) −3 . Weak charge effects were detected in the diffusion phenomenon of POD molecules in 100% H 2SO 4. The data on flow birefringence and diffusion-viscometric analysis show the absence of aggregation of POD molecules in 100% H 2SO 4 and increase in the degree of expansion of the POD molecules in solution with increasing H 2SO 4 concentration up to 100%. This increase is equivalent to an increase of several times in the Kuhn segment length. The possible causes of this effect are discussed.