Relaxation‐Induced Significant Room‐Temperature Dielectric Pulsing Effects

Abstract

Thermo‐responsive dielectric materials are in urgent demand owing to the rapid development of smart electronic/electrical systems. Although different types and structures of thermally responsive dielectric materials have been continuously reported, their dielectric response behaviors all originate from thermodynamic phase transitions. Herein, it is demonstrated that structural relaxation in poly(vinylidene fluoride) (PVDF), a non‐thermodynamic phase transition, can induce a significant thermal dielectric pulse at room temperature. The dielectric pulse strength of up to 6.3 × 105 at 20 Hz, with a dielectric pulsing temperature of 24 °C, is achieved from polyethylene glycol (PEG)‐PVDF coaxial nanofibrous films (PVDF@PEG), fabricated via a continuous blow spinning method. Moreover, the films exhibit excellent flexibility, adjustable strength and toughness, switchable hydrophilicity/hydrophobicity, and effective thermal management capability. The relaxation‐induced dielectric pulsing effect, outstanding multifunctionality, and simple preparation combine to promote further scalability and prospects of PVDF@PEG. In particular, the work contributes to the discovery of the relaxation‐induced dielectric response mechanism, which provides a new strategy for the generation of thermo‐responsive dielectric materials.

Melt‐reprocessable linear low‐density polyethylene/cyclic olefin copolymer blends with low dielectric constant and low thermal expansion

“…This also suggests the suppression of dipoleorientation polarization due to the introduction of COC. 46,47 The higher the COC content, the lower the dielectric loss, which is also related to the nonpolar, rigid molecular structure of COC. The effect of temperature on the dielectric properties of the LLDPE and LLDPE/COC at 10 4 Hz is shown in Figure 3c,d.…”

Hydrogen Bond Reorganization‐Enabled Dielectric Pulsing Effects in Polar Polymers

“…Consequently, the dielectric constant of PVDF/PEG dramatically increases, driven by the significant enhancement of interfacial polarization. [18][19][20][21]27,28,[49][50][51][52][53][54][55][56][57] In the second step, from 30 to 60 °C, corresponding to the part where the dielectric constant plummets, the hydrogen bond between PVDF and PEG is broken, evident from the blue shift of C─F, i.e., the enhancement of bonding energy (Figure 2f). This weakening of the interaction between PVDF and PEG contributes to a reduction in interfacial polarization, causing the dielectric constant to return to a low state.…”

“…[5][6][7][8][9][10][11][12] Extensive research has been conducted on manipulating the dielectric response behavior in various dielectric materials using external stimuli. The results indicate that, under thermal stimulation, the dielectric constant of thermo-responsive dielectric materials that may meet the above application requirements can undergo bistable, [13][14][15][16][17][18][19][20][21][22] linear, [23] pulsed, [24][25][26][27][28] or other response forms. [29,30] This phenomenon is called thermo-responsive dielectric behavior.…”

“…However, most dielectric-responsive materials cannot be prepared through a continuous and efficient process, and most do not have good mechanical or even self-supporting properties, which limits the potential engineering applications of many thermoresponsive dielectric materials. [14][15][16][17][18][19][20][21][22][24][25][26][27]29,30] In our recent study, [28] we prepared poly(ethylene glycol) (PEG)-poly(vinylidene fluoride) (PVDF) core-sheath nanofibers by solution blow spinning (SBS) method, which provided a solution for the continuous, efficient, and cost-effective preparation of thermo-responsive dielectric materials with good mechanical properties. In the above study, the activation energy of PVDF molecular chain motion was reduced through PEG plasticization, which induced 𝛼 c relaxation at crystal edge defects and promoted interfacial polarization and dipolar polarization, successfully triggering the room temperature dielectric pulsing effect.…”

An Overview of Phase Change Materials and Their Applications in Pavement

“…Another application in this area is a reduction of heating loads for rooms with air-conditioners [18]. It is also worth mentioning modern applications for these materials such as thermo-responsive dielectric switching/pulsing materials and temperature-sensitive electrical switching materials [41,42]. This kind of solution has potential in applications of next-generation smart electronic/electrical technology, including temperature sensors, smart switches, phase shifters, and varactors [41,42].…”