DIELECTRIC-RELAXATION STUDIES OF BISPHENOL-A POLYCARBONATE N,N'-BIS(3-METHYLPHENYL)-1,1'-BIPHENYL-4,4'-DIAMINE SOLID-SOLUTIONS

The dielectric relaxation spectra of N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (PPB)-polycarbonate (PC) solid solutions have been studied as a function of composition. The glass transition of these mixed systems varies monotonically with composition. Analysis of the apparent activation at the glass transition temperature (T(g)) show it to be composition dependent up to 50 vol% small molecules and composition independent above this composition. The data indicate that the small molecule has a greater effect on the T(g) reorientation process of the PC than vice versa. The activation energy dependence on composition is discussed in terms of the fundamental WLF parameters. From 0 to 50% PPB dynamic behaviour is as expected, increasing small molecule concentration decreases T(g) and the apparent glass transition activation energy. Above 50% small molecules, a possible T(g) dependence of some of the WLF parameters is obtained. Line-shape analysis of the glass transition provided no information on the molecular dispersion. The sub-T(g) relaxations of this system indicate little, if any, small molecule-polymer interactions. It is shown that the addition of PPB eliminates the beta-relaxation of PC and reduces the gamma-relaxation intensity. In the former case, the disappearance of the beta-relaxation is correlated with a change of composition independence in the apparent activation energy of the glass transition. The latter is a dilution effect.