Deep Eutectic Solvent—A Novel Additive to Induce Gamma Crystallization and Alpha‐to‐Gamma Phase Transition of PVDF

Abstract

Adding additives is the most convenient and effective way to induce polar poly(vinylidene fluoride) (PVDF) crystals which exhibit excellent ferroelectronic, piezoelectric, and dielectric properties. In this work, a kind of environmentally friendly additive, deep eutectic solvent (DES), is introduced to induce the crystallization of polar phases and accelerate the α‐to‐γ phase transition, which enables the fraction of γ(γ′)‐phase crystals to exceed 90% in the PVDF/DES composite containing only 1 wt% DES. The ion–dipole interaction between PVDF and hydrogen bond acceptor in DES induces the polar molecular conformation, thus bringing about the formation of polar phase crystals. However, hydrogen bond donor promotes the dispersion of hydrogen bond acceptor in PVDF matrix, contributing to the flexibility of the composites.

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

“…The large spherulites belong to α-phase, while the small ones conform to γ-phase, indicating that the addition of DES promotes the crystallization of γphase. 37 Figure 2c shows the optical micrograph of a P-M0.5 film. As is shown in Figure 2c, the number of spherulites increases significantly in P-M0.5, suggesting that MMT silicate layer could act as a nucleation center to promote the crystallization of PVDF.…”

“…The formation of polar PVDF crystals could be attributed to the ion-dipole interaction between the cations in ChCl and F atoms in PVDF molecules. 37 Doubt may arise whether glycerol in DES can also promote the crystallization of γ-PVDF. However, as presented in Figure S1a of the Supporting Information, only α-PVDF reflections appear in the diffraction pattern of PVDF/glycerol composites, suggesting that glycerol cannot trigger the crystallization of γ-PVDF.…”

“…In contrast, the other presents weak birefringence and small size. The large spherulites belong to α-phase, while the small ones conform to γ-phase, indicating that the addition of DES promotes the crystallization of γ-phase Figure c shows the optical micrograph of a P-M0.5 film.…”

“…This is consistent with the above POM results (Figure ). The formation of polar PVDF crystals could be attributed to the ion-dipole interaction between the cations in ChCl and F atoms in PVDF molecules . Doubt may arise whether glycerol in DES can also promote the crystallization of γ-PVDF.…”

Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering

“…Since α remains the most common form of PVDF, several processes have already been explored to transform this non-polar phase into polar. These processes include mechanical stretching, polarization and electrospinning (Kitsara et al, 2015;Kitsara et al, 2017;Deng and Chen, 2021;Angel et al, 2022;Li et al, 2022;Song et al, 2022;Yuan et al, 2022).…”