The concept of molecular strain energy is defined. The temperature, crystallinity, molecular strain, and free volume dependence of the nonequilibrium glassy state in PVC is analyzed. Quenched PVC samples were (1) cycled between room temperature and 112 °C and (2) annealed below Tg followed by cycling to 112 °C. The measured spectra were subjected to digital subtraction and Fourier self-deconvolution routines to extract the amorphous-state results from competing effects. It was seen that heating a quenched glass to 112 °C produced a discontinuity Δξ″ in the slope of the 1100 cm−1 skeletal frequency versus temperature curve at Tg. The value of Δξ″ was essentially zero in all slow cooling experiments and after annealing below Tg. A small shift in frequency, Δνiso was observed during isothermal annealing. Theoretical considerations indicate that Δξ″ and Δνiso have both intra- and intermolecular contributions. It is believed that this observational technique might be used to monitor physical aging in the nonequilibrium glassy state of polymers.
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Joss et al. (1983) studied this question.
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