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
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The dependence of the dissolution temperature (Tsol) 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 Tsol of PAN. A phenomenological analogy between the tacticity dependence of the Tsol 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.
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