Abstract
Abstract A polymer of methyl methacrylate with a fractional content of isotactic triads exceeding 0.99, a viscosity-average molecular weight of about (5—6) 105 and a normal glass temperature of 47°C, is investigated at pressures up 2 kbar and in a temperature range of 9 to 190°C. The results are compared with those for corresponding conventional polymers with glass temperatures above 100°C. In the liquid state, the thermal expansivity a of iso-PMMA, the internal pressure and the reduction in internal energy upon compression are larger, whereas the compressibility K is slightly smaller at elevated temperatures. In the glassy state, both α and K are smaller. The results are in qualitative accord with the existence of a weaker molar cohesion and/or greater chain flexibility, and closer packing in the stereoregular polymer. The application of the hole theory to the liquid shows the good agreement observed for other polymers in respect to the thermal expansivity, compressibility factor, and energy change with ...
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