Conformational mobility of 1,2-di-(p-bromophenyl)ethane dispersed in polymer matrices: Correlations with relaxation transition phenomena and free volume distribution in glassy polymers

Abstract

Conformational mobility of 1,2-di-(p-bromophenyl)ethane (DPBPE) introduced into glassy poly(vinyl chloride) (PVC) and poly(methyl methacrylate) (PMMA) matrices has been studied by infrared absorption spectra. For both systems under investigation the freezing of the trans-gauche conformational transitions in DPBPE has been found. The temperatures of freezing of the conformational equilibrium (Tf) have been determined: 276±8 (PVC) and 326±18 K (PMMA). The Tf values are correlated with the secondary relaxation transition temperatures of the pure polymers. In the view of the obtained data, the processes responsible for the relaxation transitions in PVC and PMMA are analysed. The volume of the conformationally mobile group of DPBPE (108.2 Å3) was found to be close to the free volume entity sizes of the polymers, measured at Tf temperatures by positron annihilation lifetime spectroscopy.