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

The phase transitions and thermophysical characteristics of poly[bis(trifluoroethoxy)phosphazene] were studied by dilatometry. An increase in temperature T of transition from crystalline state of the polymer to mesophase and substantial increase in the temperature range of mesomorphic state under elevated pressure was observed. The enthalpy and entropy of the transition decrease when the pressure increases. In the transition from crystalline to mesomorphic state, the thermal expansion coefficient and compressibility experience increases. High pressure causes a decrease in thermal expansion and compressibility of mesophase and brings those to the values comparable to the characteristics of crystalline polymer. It is shown that at low pressures the thermal expansion and compressibility of polymer mesophase are close to those of polyethylene melt.