高极性、低模量介电弹性体的合成及力电耦合性能

Preparation and electromechanical coupling properties of high polarity and low modulus dielectric elastomers

介电弹性体在人工肌肉、柔性传感、健康监测和能量收集等领域拥有广泛的应用前景.目前,介电弹性体存在介电常数低、模量高、黏弹性高等缺点,导致驱动电场大、机械损耗大.为了实现介电弹性体驱动器和传感器的高驱动应变、灵敏机电响应,本研究提出了一种液体丁腈橡胶(LNBR)与丙烯酸丁酯(BA)和丙烯腈(AN)增塑制备高介电常数弹性体的方法.采用光固化法,将极性基团氰基引入聚合物网络中,合成了一种均相PAN/PBA/NBR(PPN)介电弹性体,提高介电常数(10.13@10 kHz)的同时,有效降低了弹性体的杨氏模量(96.47 kPa).与VHB和PBA相比,PPN的介电常数分别提高了2.3和1.2倍.PPN驱动器在低电场下能产生大的驱动应变(11.4%),且PPN传感器具有高灵敏度和快速响应的优势,可以实现人体运动监测.此外,该制备策略简单方便,可大规模生产,在柔性驱动和传感方面有着广阔的应用前景.

Dielectric elastomers(DEs)are widely used in artificial muscles,soft sensing,health monitoring,and energy harvesting.Most DEs suffer from low permittivity,high modulus,and viscoelasticity,leading to high driving electrical fields and large mechanical loss.A common strategy to increase the permittivity of elastomers is to incorporate fillers with a high dielectric constant into the elastomer matrix,including conductive particles,ceramic particles,TiO2,and so on.However,a high concentration of fillers makes the elastomer stiff and usually causes premature breakdown.Adding liquid metal,ionic liquid,plasticizer,etc.,into the elastomer matrix is a typical way to decrease the Young’s modulus.Nevertheless,liquid metal is prone to react with water and oxygen,and electrons from liquid metal are easy to migrate,thereby increasing dielectric loss.Conductive ionic microdroplets can generate space charge polarization under an external electric field,thus effectively improving the dielectric constant of composite materials,but the ionic liquid/elastomer system is difficult to prepare on a large scale.The poor compatibility between the plasticizer and the matrix may result in severe leakage of plasticizers under a harsh or multi-cycled environment,which limits the long-term use of DEs in everyday environments.In a word,most strategies aimed at contributing to the improvement of one performance aspect of dielectric elastomers may cause the degradation of others.The design and preparation of high-quality dielectric elastomers remains a challenging problem.In this study,we demonstrate a valuable strategy to produce dielectric elastomers with high permittivity and low viscoelasticity.The macromolecular plasticizer liquid nitrile butadiene(LNBR)was incorporated into the polyacrylate elastomer to prepare the homogeneous PAN/PBA/NBR(PPN)dielectric elastomer.Butyl acrylate(BA)and acrylonitrile(AN)are used as polymerizable monomers to mix with liquid NBR uniformly,and then polymerized in situ to obtain homogeneous PPN.On the one hand,the NBR chain can weaken the strong dipole-dipole interaction between the adjacent side groups of PBA and PAN,resulting in low Young’s modulus and low mechanical loss.Secondly,the interface is difficult to damage when the PPN elastomer is subjected to large deformation because the PPN elastomer is homogeneous,and the molecular chain remains locked in the matrix structure,therefore the droplet leakage problem will not occur.On the other hand,the addition of acrylic ester and strong polar group C≡N in AN improves the dielectric constant of the elastomer.This preparation method has the advantages of low cost,being simple and fast,and the paste can be photocured,which is conducive to large-scale roll-to-roll production.We finally obtain PPN dielectric elastomers with high dielectric constant(10.13@10 kHz),low dielectric loss(0.08@10 kHz),low viscoelasticity(tanδ=0.29),and high elastic constant(k value of 106.17 MPa^(‒1)).Compared with VHB and PBA,the dielectric constant of PPN is increased by 2.3 and 1.2 times,respectively.We also explored its sensing and driving aspects.At low driving electric fields,PPN exhibits higher actuation performance than existing DE drivers(such as VHB),producing 11.4%large area strain at 9 V/μm.The PPN sensor responds quickly to force signals and enables human motion signal monitoring,showing long-term stability over 125 sensing cycles.Experiments demonstrated that PPN elastomer holds promise for its characteristics of high sensitivity,large driving strain,long-term stability,and large-scale preparation.It holds promise for broad application prospects in sensing fields such as electronic sensory skin and motion control sensing in the future.