Enhanced Temperature Stability of High Energy Density Ferroelectric Polymer Blends: The Spatial Confinement Effect

Abstract

ever-increasing requirement for high energy density, [1][2][3][4] especially when incorporating with further material modification through nanocomposites, [7][8][9][10] blending, [11][12][13][14][15][16] laminated structure, [17][18][19][20][21] cross-linking, [22,23] and so on.Nevertheless, the state-of-the-art PVDF-based ferroelectric polymer usually exhibits mediocre temperature stability in energy storage performance, which cannot fully satisfy the applications at elevated temperature caused by the energy consumption or nearby heat sources. [24][25][26] These polymers commonly possess glass transition temperature (T g ) far below room temperature (as shown in Table S1, Supporting Information), which helps to enhance the energy density but sacrifices temperature stability. The molecular motion in ferroelectric polymers can be activated above T g , which promotes polar molecules orientation under external stimulus evidenced by a sudden increase of permittivity at T g . [23,27] Consequently, ultrahigh energy density (about 4-35 J cm −3 ) for PVDF-based polymers has always been reported at room temperature above T g . [1][2][3] On the other hand, low T g is detrimental to temperature stability of energy storage in PVDF showing dramatical degradation at elevated temperatures. Because rubbery-state amorphous region above T g , which manifests itself as loose chains with increased free volume, becomes vulnerable to temperature rise. [25,26,28] Recent investigations even point out that high-T g non-ferroelectric polymers can maintain an energy density around 0.5-1.8 J cm −3 up to a fairly high temperature. [25,26,29] Nonetheless, for ferroelectric polymers, it remains a considerable challenge to achieve high energy storage performance at the elevated temperature.In this work, we propose to design a strategy for stabilizing high energy density of ferroelectric polymer (PVDF) over a wide temperature range by blending with a miscible high-T g polymer (polymethyl methacrylate [PMMA]). The blending material forms a alternating lamellar structure consisting of high-polarization crystalline regions and mixed amorphous regions. It is found that this special morphology can induce a spatial confinement effect of chain mobility and structural change at elevated temperatures. Accordingly, the associated Thermal stability of polymer structure is a key to achieve stable energy density at elevated temperature for ferroelectric-polymer-based capacitors. Here, a poly (vinylidene fluoride) / polymethyl methacrylate (PMMA) blend with a stabilized spherulite structure displaying steady energy density around 7.8-9.8 J cm −3 across the temperature range up to 70 °C is reported, which outperforms most neat ferroelectric polymers at elevated temperature. The microstructure of the blend observed by atomic force microscopy exhibits an alternating lamellar structure (crystalline/mixed amorphous layers) within spherulites, which might be rationalized by PMMA being gradually expelled from the spherulite and finally staying between PVDF lamellae ...

Enhanced High‐Temperature Dielectric Properties of Poly(aryl ether sulfone)/BaTiO3 Nanocomposites via Constructing Chemical Crosslinked Networks

“…[8][9][10][11] Recently, by integrating the excellent dielectric properties of BaTiO 3 (BT) and Polyvinylidene fluoride, researchers have improved the dielectric properties of the dielectric materials, which have high dielectric constant (>10) and high breakdown strength (>400 MV m −1 ). [12] This is beneficial to increase the energy storage density of the polymer composites. However, due to its large hysteresis loss and relatively flexible polymer molecular chain (lower glass transition temperature), these composites are difficult to be applied in a high temperature environment.…”

Ferroelectric Materials for Solar Energy Scavenging and Photodetectors

“…To improve the temperature stability of energy storage performance of PVDF, a blending method was applied on PVDF and polymethyl methacrylate (PMMA), then obtained a material compounded from high-polarization crystalline regions and mixed amorphous regions. [17] The AFM height profile of the PVDF-PMMA blend is shown in Figure 2c 3 , the PVDF (yellow) is intertwined with PMMA (dark) and forms an amorphous layers structure. The energy density and efficiency of PVDF-PMMA as high as 9.8 J cm −3 and 67.8% under 70 °C, which exceeds most ferroelectric polymers.…”

“…c 3 ) AFM height profile of PVDF and PMMA blend. Reproduced with permission [17]. Copyright 2019, Wiley-VCH.…”

Confinement effects at nanoscale in natural rubber composites: Influence on macroscopic properties

“…But still both micro as well as nanocomposites are not devoid of deterioration in properties and structural defects. This depends on the mode of filler dispersion in the matrices 7–10 and therefore modification of filler surfaces is often practiced prior to compounding.…”

“…Confinement effects of elastomer molecules in composite systems can regulate composite properties and thus their applications 10,11 . The orientation of elastomer chains in the presence of micro as well as nanofillers is one of the key factors affecting mechanical properties.…”