| With the gradual deepening of people’s understanding of the relationship between material structure and performance,more and more smart materials with different functions and application scenarios have come out one after another.These continuously born smart materials are providing the possibility of positive change for human society.Among them,temperature-responsive dielectric materials have become a research hotspot due to their unique,controllable,and designable temperature response behavior and important application potential.At present,temperatureresponsive dielectric materials are mainly ferroelectric and antiferroelectric small molecules.In recent years,non-ferroelectric phase change induced dielectric response behavior has attracted attention,and it is expected to become a new generation of smart switching materials.Its preparation strategy,material structure and dielectric response mechanism are quite different from ferroelectric dielectric response materials.People have not yet deepened the understanding of the relationship between its structure and dielectric response performance.In this paper,based on the principle of dielectric response induced by changes in the structure of polar molecular aggregates,a simple,low-cost and efficient strategy is used to prepare thermally responsive fiber-based dielectric polymer composites.Polyethylene glycol(PEG)is introduced into high-dielectric constant polyvinylidene fluoride(PVDF)fiber through electrospinning technology.Using this process,we prepared a series of PEG composite membranes to explore the effect of nonferroelectric phase transition on composite dielectric response characteristics and the response mechanism.First,pure PVDF electrospinning membranes were prepared by electrospinning,and then PEG800/PVDF electrospinning composite membranes and PEG800 and nonferroelectric materials(PA-66)electrospinning composite membranes were prepared by coaxial electrospinning..The results show that the addition of the phase change material PEG has a significant effect on the dielectric response.The dielectric constant of the PA/PEG electrospun membrane is increased from 2.6 to 16.1 in the temperature range of-10-10℃;while the PVDF/PEG In the temperature range of-10-10℃,the dielectric constant of the electrospun membrane increases from 8 to 55.9.The ferroelectric material PVDF also has an impact on the dielectric response performance of the composite system.The on-off ratio of 6.9875 is greater than the on-off ratio of PA/PEG electrospun membrane of 6.1923,which also proves that the ferroelectric fiber shell has a certain amplifying effect on the dielectric switch performance.Subsequently,this paper also explored the influence of the number of fiber membrane layers on the dielectric response performance.The influence of the number of layers on the dielectric response performance is similar to the seepage model,and there is an optimal value for the dielectric performance.For the test results of this paper,the PEG/PA composite film has the largest on-off ratio and the best dielectric response performance when it is a single layer;the double-layer PEG/PVDF has the largest dielectric switch ratio and the best dielectric response performance.P(VDF-TrFE)and PEG/PVDF electrospun fiber membrane are compounded by solution coating method,and vacuum-dried to obtain a ternary composite membrane,which enhances the processing performance of the fiber membrane to meet more needs.The data shows that the dielectric constant of the PEG/PVDF/P(VDF-TrFE)composite membrane increases from 13 to 74.3 during-20-25℃.The on-off ratio of the terpolymer membrane reaches 5.7154,which is smaller than that of the electrospun membrane.6.9875,but the initial dielectric constant of the composite membrane is significantly higher than that of the electrospun fiber membrane,which is mainly attributed to P(VDF-TrFE).Glycerin(GLY),a hydrogen bond regulator,is introduced,and PEG is processed by adding GLY with different mass fractions to form a GLY/PEG system with different numbers of hydrogen bonds.GLY successfully combined with PEG and formed a large number of hydrogen bonds.GLY and PEG formed hydrogen bonds to make the interface between PEG and PVDF more tightly bound,the dielectric constant also increased,and the dielectric switching ratio was significantly increased,7% The dielectric switch ratio of the composite membrane of GLY/PEG/PVDF/P(VDF-TrFE)is up to 18.47.In this study,the three aspects mentioned above are used to investigate the influence of the fiber shell layer,the composite membrane matrix,and the hydrogen bonding effect on the corresponding dielectric properties.The directional polarization caused by the melting of the polar phase change material PEG increases the effective dipole moment,which is the main factor for the increase in the dielectric constant;the ferroelectric fiber shell also makes the composite system dielectric due to its high polarization strength.The constant has been greatly improved.The polarization strength of the polymer matrix of the composite membrane is an inherent property,and there is basically no significant polarization enhancement effect,so it has no effect on the dielectric response performance;and the introduction of a large number of hydrogen bonds makes the composite system The combination is tighter and the interface phase is strengthened.Since the hydrogen bond effect is much smaller than the chemical bond effect,the directional polarization produced by melting and the interface polarization have a synergistic effect,and the on-off ratio is significantly increased.Dielectric switch materials allow us to design smart materials sensitive to stimuli through simple,low-cost and efficient strategies.In addition,by studying the phase transition characteristics of composite materials,we can use PEGs with different molecular weights to adjust the temperature of the dielectric switch to meet more usage requirements.Considering the preferred room temperature dielectric transition,the relatively sensitive increase in dielectric constant,good shape stability and low cost,nanocomposites,as an innovative thermally responsive dielectric material,have great potential in stimulus-responsive smart devices. |
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