Thermodynamics of polymer blends based on poly(epsilon-caprolactone)/poly(vinyl methyl ether)

The miscibility of the system poly(epsilon-caprolactone)/poly(vinyl methyl ether), PCL/PVME, was investigated using differential scanning calorimetry (DSC), solution calorimetry, optical microscopy (OM), Fourier transform inf rared spectroscopy (FTIR), dilatometry, and internal pressure. The system i s semicrystalline and the PCL crystallinity is sensitive to the composition of the: blend and to the thermal; treatment performed. The presence of a s ingle glass transition temperature for all compositions is considered as an index of miscibility in the amorphous phase, but the evolution of crystall ization and melting peaks shows that phase separation phenomena occur upon heating the system just above the PCL melting point, according to a 'lower critical solution temperature' behaviour. The process of mixing is markedly endothermic and this means that the system is immiscible in the liquid pha se, i.e. just above the PCL melting point. FTIR experiments demonstrate the absence of specific interactions between the two components. OM was used c ombined with DSC to investigate the occurrence of a melting point depressio n which can be used to evaluate the chi(12) parameter. Finally, dilatometri c and internal pressure techniques were used to obtain the required data fo r the evaluation of the interaction parameter, chi(12) following the Patter son approach. The resulting value of the chi(12) parameter is always positi ve and higher than the critical value in the considered temperature range. This behaviour indicates, too, that the system is not miscible when it is h eated above the PCL melting point.