THE EFFECT OF PRESSURE ON THERMOPHYSICAL CHARACTERISTICS OF POLY[BIS(TRIFLUOROETHOXY)PHOSPHAZENE]

The phase transitions and thermophysical characteristics of poly[bis(t rifluoroethoxy)phosphazene] were studied by dilatometry. An increase i n temperature T of transition from crystalline state of the polymer to mesophase and substantial increase in the temperature range of mesomo rphic state under elevated pressure was observed. The enthalpy and ent ropy of the transition decrease when the pressure increases. In the tr ansition from crystalline to mesomorphic state, the thermal expansion coefficient and compressibility experience increases. High pressure ca uses a decrease in thermal expansion and compressibility of mesophase and brings those to the values comparable to the characteristics of cr ystalline polymer. It is shown that at low pressures the thermal expan sion and compressibility of polymer mesophase are close to those of po lyethylene melt.