Ionic Liquid Assisted α–γ′ Phase Transition of Poly(vinylidene fluoride) Thin Films

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.

Achieving synergistic improvement in dielectric constant and energy storage properties of all-organic liquid crystal molecule/PVDF composites

“…Furthermore, the characteristic peaks at 614 cm À1 , 763 cm À1 and 1402 cm À1 are attributed to the nonpolar a phase of the PVDF, and the characteristic peaks of the polar g phase of PVDF are observed at 811 cm À1 , 833 cm À1 and 1234 cm À1 . [44][45][46] The results suggest that the a and g phases coexist in the pristine PVDF sample and all the 5CB/PVDF composite samples, which matches the result of POM. It can be clearly noted that the intensity of the g-phase peak decreases at first and then increases following the incremental content of 5CB due to the polar intermolecular interaction between 5CB and PVDF.…”

Synergistic Improvement in γ-Phase Content and Dielectric Properties of PVDF/Deep Eutectic Solvent/Montmorillonite Composite Films

“…As is seen from Figure 5a, the WAXD pattern of pure PVDF crystallized at 150 °C for 60 min displays the (100), (020), and (110) diffractions of α-PVDF located at 2θ = 17.6°, 18.4°, and 20.0°, respectively. 25 These α-PVDF reflections also appear in the diffraction pattern of P-M0.5, suggesting that α-PVDF crystals are dominant in P-M0.5. That is, the addition of MMT has not efficiently promoted the formation of polar PVDF crystals.…”

Development of polar phases in ferroelectric poly(vinylidene fluoride) (PVDF) nanoparticles

“…This has been attributed to the enhancement of TT conformation due to the interaction of PVDF CF 2 groups with the charged surfaces of the additives. Also, the exposition of thin films to ionic liquids and temperature produces the γ polar phase in PVDF [15]. Polar phases in PVDF have been reported on nanoconfined systems [16,17].…”