Glass transitions in ionic polymers

Abstract

The glass transitions of an ionic polymer in bulk have been studied as a function of the counterion for various homo‐ and copolymers. It is shown that the glass transition temperature can vary by as much as 530°C., from −10°C. for the nonionic material to +520 for Ca²⁺ or Zn²⁺ substituted polymer. From simple electrostatic considerations, it is shown that a linear correlation should exist beween the glass transition and the ratio of the cation charge, q, to the internuclear distance, a, between cation and chain anion; for this particular material (the polyphosphate chain) the relation is T_g = 625(q/a) −12 where q is in units of one electron and a is in A. If the data are interpreted in the light of the Gibbs‐DiMarzio theory, it is seen that both the chain stiffness and the intermolecular energy increase in an approximately parallel manner as q/a increases.