Optical properties of polyacrylonitrile molecules in N,N-dimethylacetamide

The present paper deals with the investigations of hydrodynamic properties of PAN, as an engineering material with increasing technological interest. The methods of translational diffusion, velocity sedimentation and viscometry are employed. At first time, optical anisotropy of the PAN molecule was determined with flow birefringence technique which is very sensitive to intramolecular structure. The PAN sample with molecular weight of 9x10(5) and low stereoregularity was studied in dilute solution in N,N-dimethylacetamide. Intrinsic viscosity was calculated according to Huggins equation from the dependence of reduced viscosity on concentration of solution. Molecular mass was determined with Svedberg's equation. The heterogeneity parameter was evaluated by the absolute method of analytical ultracentrifugation. Translation diffusion was investigated using a gradient method in a cell Teflon in the Tsvetkov's interferometric diffusometer. The flow birefringence measurements were made in titanium dynamooptimeter and the Hg-lamp was used as a light source. The sign of the effect and the stress optical coefficient were determined. The role of the micro and macro form effects in flow birefringence is discussed. The intrinsic optical anisotropy (-3.3x10(-25)) cm(3) of the chain unit of the PAN molecule is attributed to structural features of the polymer molecule and anisotropy of the cyano-groups.