Enhancing the Alpha-To-Gamma Phase Transition of Poly(vinylidene fluoride) via Dehydrofluorination Modification

Due to the high activating energy, it is very difficult to initiate the alpha-to-gamma phase transition of poly-(vinylidene fluoride) (PVDF), resulting in an extremely slow transition rate. Here, introducing a small number of double bonds into the PVDF molecular chains through dehydrofluorination is demonstrated to markedly decrease the activating energy and enhance the phase transition efficiency. It is found that the introduced double bonds during the dehydrofluorination reaction accelerate the alpha-to-gamma phase transition, which is reflected by the shortened induction period and increased transition rate. The alpha-to-gamma phase transition in PVDF modified with double bonds occurs mostly from the nuclei of alpha-spherulites rather than from the scarce boundaries initiated by gamma-spherulites as in unmodified PVDF. Comparative analysis reveals that the energy storage performance of gamma-PVDF films prepared through the phase transition surpasses that of alpha-PVDF ones. Compared to alpha-PVDF, the energy storage density of the modified gamma-PVDF exhibits a remarkable enhancement of 181%, while the energy storage efficiency experiences a notable improvement of 124%. Consequently, a molecular modification strategy for the alpha-to-gamma phase transition is introduced, enabling efficient production of gamma-PVDF with enhanced energy storage properties and positioning it as an ideal material for driving technological advancements in electronic devices, electric vehicles, and renewable energy sectors.