A segment concept in the dissolution of stereoregular isotactic: polyacrylonitrile into three dinitrile solvents, CN-(CH2)(n)-CN (n=1, 2, and 3), at elevated temperatures

摘要

The dependence of the dissolution temperature (T-sol) of isotactic polyacrylonitrile (PAN) on tacticity was studied for three dinitrile solvents. A linear relationship was obtained in the inverse plots of the tacticity dependence of the T-sol of PAN. A phenomenological analogy between the tacticity dependence of the T-sol of isotactic PAN and the molecular-weight dependence of the glass-transition temperature of amorphous polystyrene is discussed from a thermodynamic point of view. The linear relationships in both phenomena are explained in terms of a common mechanism: a breakdown of thermodynamic competition, enthalpy, and entropy through the segment mobility. The significance of segment concept and molecular mobility at elevated temperatures are discussed. [References: 12]