Energy barriers for dipole moment flipping in PVDF-related ferroelectric polymers

Abstract

Energy barriers for flipping the transverse dipole moments in poly(vinylidene fluoride) (PVDF) and related copolymers and terpolymers are predicted using the nudged elastic band method. The dipole moments flip individually along the chain, with an order and energy barrier magnitudes (0.1-1.2 eV) that depend on the chain composition and environment. Trifluoroethylene (TrFE) and chlorofluoroethylene (CFE) monomers have larger energy barriers than VDF monomers, while a chain in an amorphous environment has a similar transition pathway as that of an isolated molecule. In a crystalline environment, TrFE and CFE monomers expand the lattice and lower the energy barriers for flipping VDF monomers. This finding is consistent with experimental observations of a large electrocaloric effect in P(VDF-TrFE-CFE) terpolymers.

Physical reality of the Preisach model for organic ferroelectrics

“…The characteristic switching time dependence on the setting field (Supplementary Figure 7c ) in boundary case A shows an exponential dependence and can be successfully fitted using Eq. ( 5 ) with w b = 0.2 eV nm −3 , which is twice higher than for BTA due to higher rotational energy barrier of the −CH 2 −CF 2 − chains, compared to the H-bonded O∙∙∙H–N network of BTAs 55 . The switching time values in case B reach a plateau value t 0 of around 0.2 ms, which does not exceed the minimum switching time of case A .…”

Multiscale-structuring of polyvinylidene fluoride for energy harvesting: the impact of molecular-, micro- and macro-structure

“…T-trans; G-gauche. 61 Measurements of the ferroelectric and piezoelectric properties can be undertaken by polarisation-electric eld measurements, piezo-response force microscopy and second harmonic generation microscopy.…”

“…4b. 61 The crystalline structure of PVDF has been studied during a micro-injection process and in the presence of polar additives. 74 In contrast to crystallisation in the static state, the application of high stress during micro-injection promotes the formation of b-phase.…”

“…31 The T c of b-PVDF is typically $170 C (ref. 87) and the introduction of a co-monomer to the polymer chains can restrict the degree of crystal growth and form nanosized crystalline domains, 61,85 which increases the inter-chain distance and dipolar mobility, and decreases the T c . For example, a low T c of 105 C was measured for a copolymer of 70/30 composition ratio.…”

Electrospun Polyvinylidene Fluoride-Based Fibrous Scaffolds with Piezoelectric Characteristics for Bone and Neural Tissue Engineering

“…For instance, PVDF with good biocompatibility and processability can be used to make monofilament suture material for cardiovascular surgery [52]. PVDF is a semicrystalline polymer having five crystalline polymorphs, including α-, β-, γ- δ- and ε-phases [2,53,54,55]. Among these, the β-PVDF-phase exhibits excellent piezoelectric and ferroelecric properties.…”