Room-temperature Tunable Dielectric Switching Composites Based On Non-Ferroelectric Phase Transition

Thermally responsive dielectric materials can be reversibly converted between high and low dielectric states near specific temperatures,and their unique thermally responsive dielectric behavior is of great research and application value.In addition to ferroelectric phase transitions,non-ferroelectric crystallization-melting phase transitions may also induce dielectric response behavior.An in-depth understanding of the non-ferroelectric phase transition-induced dielectric-temperature response law and mechanism at the micro/nano and molecular levels is expected to lead to innovative means of dielectric-responsive material design and preparation.(1)First,to address the key limitations of dielectric switching materials such as poor integration of remarkable dielectric switching properties,promising scalability,and low cost.We demonstrate a generic solution to these problems to achieve a good cost/performance balance.By mixing ionic liquids(ILs)with polyethylene glycol(PEG),an all-organic composite enables an ultrahigh dielectric switching ratio above 320.6 at 34.2 Hz,almost 100%dielectric constant retention after 500 cycles,the highest attainable to a～35°C wide thermal hysteresis loop,and tunable dielectric transition temperature.Also,the PEG/ILs can defeat the conflict of dielectric switching properties versus cost,namely impressive dielectric switching properties are achieved through simple mixing of commercialized components without solvent.The findings offer promise for highly efficient,scalable,low-cost,and environmentally friendly preparation of high-performance room-temperature dielectric switching materials.(2)Second,to address the two crucial challenges facing thermally responsive dielectric materials:insufficient mechanical toughness and lack of the combination of promising dielectric switching properties,desired mechanical properties,and long-cycle stability.Herein,we propose a new scalable strategy for designing thermo-responsive dielectric switching materials that simultaneously integrates the individual features,such as promising dielectric switching properties,outstanding mechanical properties,and great cycle stability,into one gel,based on a new dual dielectric switching mechanism induced by interfacial structure evolution.The ionic gel can readily achieve a superb combination of distinct reversible dielectric bistability,a high dielectric switching ratio above 150,a～15°C wide thermal hysteresis loop,tunable room-temperature dielectric transition behavior,impressive high ductility,desirable high mechanical strength,record-high stability of at least 1000 cycles.Such an all-in-one design enhances the adaptability to multiple application scenarios,durability,and lifetime of the dielectric switching gels.Together with the facile fabrication process and recyclable thermoplastic system,thereby contributing to cost and energy saving,our research provides a feasible and sustainable strategy for constructing highly desirable thermo-responsive dielectric switching materials.(3)Finally,in order to break the limitations of existing dielectric switching mechanisms to achieve ultra-high dielectric switching ratios.Here we report an unparalleled dielectric switching effect in a water-in-oil emulsion system,caused by dual polarization synergy below the dielectric transition temperature in concert with suppression of the electrode polarization above the dielectric transition temperature.The synergistic dielectric switching effect of interfacial polarization and electrode polarization endows the emulsion with unprecedentedly high dielectric switching ratios.The highest room temperature dielectric switching ratio of this emulsion system up to 2.86×10~6 at 20 Hz,is four orders of magnitude higher than the highest switching ratio reported so far.The unparalleled high dielectric switching ratio,reliable cycle stability,good frequency adaptability,and satisfactory scalability make the inorganic salt solution/octadecane emulsions potentially excellent candidates for high-sensitivity room-temperature smart switching or sensing devices.