Spontaneous elongation of acetate fibres in dimethyl sulfoxide vapors: dynamics, structure, energetics

Abstract

The effect of a spontaneous change in the size (elongation-partial retraction) of di- and triacetate fibres in DMSO vapors in the 19-60°C range, accompanied by initiation of orientation events in the polymer matrix was detected. Sorption of DMSO vapors by the polymer in self-deformation of the acetate fibre does not obey Fick’s law and is described by extremal swelling curves that indicate the multistage character of the reaction of the sorbate vapors with the polymer. The energetics of spontaneous elongation of cellulose acetate in DMSO vapors was investigated, and the specific work of self-deformation and “negative” longitudinal viscosity were determined. The values of the specific heat was typical of transitions from the isotropic to the LC state. It was found that the stereomeric structure of the polysaccharide changes during a cyclic change in the size of the fibre, confirmed by inversion of the specific optical rotation sign. The data obtained can be described in terms of phase and conformational transitions and the mechanism of reaction of the polymer with the solvent vapors forming the LC phase with it.