Dilute solution properties of acrylonitrile-methyl acrylate copolymers in dimethylformamide

Abstract

Viscosities and osmotic pressures of dilute solutions of fractions of polyacrylonitrile and of copolymers of acrylonitrile and methyl acrylate, and of polymethyl acrylate in dimethylformamide have been measured at different temperatures. Temperature coefficients of intrinsic viscosity [η] are negative and those for polyacrylonitrile and the copolymers are relatively large. A maximum value of —d[ η]/d T is obtained at a copolymer composition approximating to 85 per cent by weight of acrylonitrile. Values of the polymer-solvent interaction parameter χ 1 are a minimum at this composition and increase with increasing temperature. These results are considered in terms of chain flexibility and polymer—solvent interaction. It is concluded that the negative temperature coefficients of [η] and their variation with copolymer composition are consequences of polymer—solvent interaction rather than chain stiffness.