Influence of Aliphatic Polyesters on the γ Phase Crystallization of Poly(vinylidene fluoride)

Abstract

The polar phase of poly(vinylidene fluoride) (PVDF) is attractive for fabricating electroactive devices. However, the nonpolar α form is thermodynamically most accessible during the crystallization process. Here three types of aliphatic polyesters are chosen for blending with PVDF to explore their effect on inducing polar γ phase crystallization of PVDF. It is found that the ability of γ phase nucleation of PVDF enhances as the blend ratio of aliphatic polyesters and isothermal crystallization temperature increase. Poly(butylene succinate) (PBS) with highest melting temperature shows the highest ability for inducing γ phase crystallization. For example, the pure γ phase has been obtained under an appropriate blend ratio and isothermal crystallization temperature in PVDF/PBS blends. This is attributed to the hydrogen bonding interaction of H atoms in PVDF with carbonyls in PBS and the slow diffusion rate of PBS chains in PVDF. The addition of PBS lowers the folding surface free energy of the γ phase. This work offers a reference for selecting a suitable blending system to obtain pure γ phase PVDF and contribute to a better understanding of the relationship between intermolecular interaction and polymorphic phase selection.

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

“…Many effective methods have been developed to promote the α–γ phase transformation or induce the direct crystallization of γ-PVDF, including solvent casting, addition of specific fillers or aliphatic polyesters, − coating of ion liquids, and application of porous alumina template as well as high pressure or shear stress . As for most of the reported methods to fascinating the α–γ phase transition process, there appear obvious limitations, such as complex process and lower break down electric field.…”

Validity of –CF2 Band Shift in Poly(vinylidene fluoride) as an Indicator for the Ion–Dipole Interaction

“…Poly­(vinylidene fluoride) (PVDF) exhibits five different crystalline phases, i.e. α, β, γ, δ, and ε, among which the polar γ- and β-phases are most attractive and desired due to their excellent pyro-, piezo-, and ferroelectric properties. − The nonpolar α-phase is, however, generally obtained during crystallization from the melt rather than the polar phases. Therefore, many strategies have been developed to produce the polar γ- or/and β-phases of PVDF, such as self-seeding, , incorporation of nucleation agents, − induction by ion–dipole interaction, − and utilization of an external field including stress, high pressure, thermal field, and electric field. − Among them, the introduction of long-chain quaternary ammonium salts into PVDF to form ion–dipole interactions can effectively trigger the crystallization of PVDF from melt into the polar phases.…”

Various Solvent‐Binder Compositions and their Crystalline Phase for Optimal Screen‐Printing of NMC Cathodes

“…Methods such as the selection of PVDF copolymers, solution casting of pristine PVDF, and incorporation of nanofillers have proven successful in promoting the electroactive (β and γ) phases of PVDF. [24][25][26] Interestingly, PVDF films that exhibit the γ phase and possess a dense microstructure have been observed to perform well in energy storage applications compared to other variations, underscoring the influence of phase and structure on the material's performance. [27][28][29] Song et al demonstrated higher performance in LFP cells with an increased β phase.…”

“…The electroactive β‐phase of PVDF has been reported to be induced by electrical poling and stretching of the polymer at high temperatures. Methods such as the selection of PVDF copolymers, solution casting of pristine PVDF, and incorporation of nanofillers have proven successful in promoting the electroactive (β and γ) phases of PVDF [24–26] …”