Glass temperature of copolymers

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Abstract
According to a recent theory of the glassy state, chain stiffness is the main determinant of the glass transition. In this paper the theory is applied to the problem of predicting the glass temperatures of copolymers of varying composition and therefore varying chain stiffness. It is found that a simplified treatment leads to an equation which is identical in form to the Gordon–Taylor equation but whose coefficients have a different physical significance. Evaluation of these coefficients requires knowledge of only the structures of the homopolymers. This simplified treatment can be applied to various types of copolymer systems but amounts to more of an approximation in the case of random copolymers of the addition (vinyl) type than in the case of random copolymers of the condensation type. The glass temperatures of the condensation copolymer system polyethylene adipate/terephthalate are predicted within experimental error. The average per cent deviation between theory and experiment for 10 well‐characterized vinyl type copolymer systems is found to be 6.4%. In order to illustrate the applicability of the equation to systems not normally considered as copolymeric, the glass temperatures of the polymer system poly‐n‐alkyl methyl methacrylate (varying n) are correlated.

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