ACRYLONITRILE SODIUM METHALLYLSULFONATE COPOLYMER IN DIMETHYL-SULFOXIDE - NMR APPROACH TO THE PHASE-DIAGRAM

The temperature and concentration dependences of the physical state of solutions of an acrylonitrile-sodium methallylsulfonate copolymer in dimethyl sulfoxide (DMSO) are investigated from calorimetric and NMR m easurements within the temperature range where the solvent crystalliza tion and/or polymer ordering in solution can occur. i) For solutions o f global monomeric molar fraction higher than 0.45, ordering of a frac tion (<0.15) of the polymer can occur. Temperatures of polymer melting and polymer ordering are reported. The composition of the liquid phas e coexisting with ordered polymer is found to depend on the global con centration of the solution. At low temperatures, i.e., at temperatures for which DMSO crystallizes, three phases are found to coexist: order ed polymer, crystalline DMSO and disordered solution. ii) For solution s of global monomeric molar fractions smaller than 0.45, the polymer i s disordered at all temperatures. Crystallization of pure DMSO is obse rved and the melting/crystallization curve of DMSO is determined by NM R and described with simple thermodynamic considerations.