Effect of chemical structure of amorphous polymers on heat capacity difference at glass transition temperature

The heat capacity of 21 kinds of glassy polymers, mainly synthesized in our laboratory, was measured by differential scanning calorimetry. Glass transition temperature (T-g) and the heat capacity difference between the molten state and the glassy state (Delta C-p) at T-g were evaluated. A linear relationship was obtained between Delta C-p and T-g for almost all glassy polymers including engineering plastics, in a temperature range from 230 to 520 K, except for those having large side chains and/or inter-molecular hydrogen bondings. It was suggested that configurational entropic factors must be taken into consideration for analyzing glass transition.