Relationship of First- to Second-Order Transition Temperatures for Crystalline High Polymers

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Abstract
This paper concerns an empirical linear relationship between the melting temperature T1 and the second-order or glassy transition temperature T2 for partially crystalline polymers. Two lines can be drawn, one for symmetrical polymers, the other for unsymmetrical polymers, the latter being of lower slope. These families are only approximate. It is shown for a limited group of polymers, that T2 is proportional to the cohesive energy density of the polymer. Since T1=ΔH/ΔS, it is suggested that the two families of curves arise because of differences in ΔS which depends on symmetry and chain stiffness. It is shown that T1 and T2 are linearly related with diluent as a common parameter.