Effect of temperature and solvent on hydrodynamic and optical properties of cellulose carbanilate molecules

Abstract

Two high molecular weight cellulose carbanilate (CPC) samples with degrees of substitution of 2·5 and 3·0 were examined at temperatures of 2·5 to 75° by methods of progressive diffusion, rapid sedimentation (in ethylacetate), viscometry and flow birefringence (in dioxane and other solvents). The coefficient of progressive friction of CPC molecules and dynamic flow birefringence, the same way as the intrinsic viscosity of CPC solutions, decrease with an increase of temperature. This reduction may be due to the variation of equilibrium rigidity of CPC molecules. The statistical Kuhn segment calculated from diffusion and sedimentation in ethylacetate considering the flow properties of CPC molecules approximately doubles (from 200–250 to 500 Å) with a reduction of temperature from 50 to 2·5°. Results of dynamic birefringence and viscometry confirm this conclusion and indicate that the variation of temperature or solvent may be accompanied by a variation of optical anisotropy of the CPC monomer unit. The considerable increase in equilibrium rigidity of CPC molecules with a reduction of temperature may be caused by the formation of intramolecular hydrogen bonds or a redistribution in the number of stereo-isomers of the cellulose chain.