Unveiling the impact of regioisomerism defects in the glass transition temperature of PVDF by the mean of the activation energy

Alternating two groups, CH2 and CF2, of very different polarities along the backbone chain of polyvinylidene fluoride (PVDF) leads to very interesting properties, such as ferroelectricity. However, these properties are affected by the presence of regioisomerism defects (monomer inversion) that appear during the synthesis. In this study, the influence of these defects on the glass transition temperature (Tg) is regarded. Using molecular simulation, we investigated their plasticizer effect. To highlight their role in modifying polymer chain relaxation, the activation energy (Ea) related with conformational transitions is computed. We show that a clear linear relationship can be established between Ea and Tg. Ea is then separated into different contributions associated with each type of bond. Mobility of individual segments can thus be accounted separately from the mobility of the whole chain. As a consequence, Tg of the alternate copolymer ethylene-tetrafluoroethylene (E-TFE), an isomeric polymer of PVDF, can be deduced. Tg of this copolymer is still source of discussion in the literature. The resulting value, −97 °C, is found in good agreement with some experimental data, and also with Tg extracted from simulated dilatometry. Consequently, local mobility of a polymer chain can be retrieved from the whole mobility, and vice versa. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016.