Enhancing the Alpha-To-Gamma Phase Transition of Poly(vinylidene fluoride) via Dehydrofluorination Modification
Muhua Yuan, Haijun Wang, Yuxin Wang, Ji Li, Chunlei Yuan, Xiaoli Sun, Jian Hu, Shaojuan Wang, Shouke Yan
Abstract
Due to the high activating energy, it is very difficult to initiate the α-to-γ 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 α-to-γ phase transition, which is reflected by the shortened induction period and increased transition rate. The α-to-γ phase transition in PVDF modified with double bonds occurs mostly from the nuclei of α-spherulites rather than from the scarce boundaries initiated by γ-spherulites as in unmodified PVDF. Comparative analysis reveals that the energy storage performance of γ-PVDF films prepared through the phase transition surpasses that of α-PVDF ones. Compared to α-PVDF, the energy storage density of the modified γ-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 α-to-γ phase transition is introduced, enabling efficient production of γ-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.