Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films
Zixiong Liu, Haijun Wang, Kun Liu, Huihui Li, Xiaoli Sun, Jian Hu, Shaojuan Wang, Chunlei Yuan, Shouke Yan
Abstract
In this work, a simple and efficient approach has been developed for preparing γ-PVDF films with a wide range of thickness based on the spontaneous diffusion of ionic liquids (ILs) into the α-PVDF matrix. It involves three steps: (i) preparation of α-PVDF films, (ii) surface coating of the resultant α-PVDF films with ionic liquids or quaternary ammonium solution, and (iii) annealing the surface modified PVDF thin film at a high temperature. In this way, the original α-PVDF film is then transferred into a γ-rich one through the well-known α–γ′ phase transition. The α–γ′ transition is found to be much faster and more efficient for high-temperature prepared samples. It has been further confirmed that the α–γ′ phase transition includes the induction and slow phase transition stages for low-temperature fabricated samples as well as the rapid and then slow transition stages for the samples prepared at 120 and 150 °C.