Comparative study of diluent effects on the glass transition of polyvinylchloride and phenolphthalein

Summary Some binary polymer-diluent systems, previously studied by the Authors (SCANDOLA et al., 1982), showed an unusual T_g-concentration dependence. In order to investigate the relevance of the polymeric nature of the high-T_g component in determining this anomaly, two series of mixtures having the same diluent (di-n-Butylphthalate or Tricresylphosphate) and, as the high-T_g component, either a polymer (PVC) or a low-molecular weight substance (Phenolphthalein), have been examined. A discontinuity is found, as expected, in the polymeric systems PVC-di-n-Butylphthalate andPVC-Tricresylphosphate, as well as in Phenolphthalein-di-n-Butylphthalate mixtures where, however, the deviations from the calculated T_g-composition curve are much less marked. It is concluded that the presence of a polymer is not a necessary requirement for the occurrence of the above mentioned anomaly.