| Dielectric elastomer（DE）is a kind of electroactive polymer which can respond to external electric field.It has the advantages of fast response to electrical stimulation,high electromechanical coupling efficiency and simple working principle.As an application of dielectric elastomer,the dielectric elastomer generator（DEG）,which is composed of DE film and compliant electrodes coated on its upper and lower surfaces,is a device that uses the principle of variable capacitor to generate electricity.It can convert mechanical energy into electrical energy during the process of tensile recovery,and can convert a variety of mechanical energy（such as tides,human motion,etc.）into electrical energy in nature.Compared with traditional generators,DEG has the advantages of light weight,high energy density,high conversion efficiency,long lifetime and low cost.It can be used to manufacture energy collectors and marine generators.The reported DEG devices mainly use acrylate（VHB）as DE material,which does not consider the fatigue life and has no application value,so it is necessary to develop dielectric elastomer materials with long life and high energy harvesting performance suitable for DEG.Polymethylvinylsiloxane（PMVS）has high insulation,high breakdown strength and high elasticity,but as a DE material its application is limited because of the low dielectric constant.According to previous literature reports,the introduction of polar groups into the polymer chain can increase the dielectric constant of the material by increasing its dipole polarization ability,but this may increase the electrical conductivity of the material and lead to an increase in the charge loss rate.Adding high dielectric constant ceramic fillers,such as titanium dioxide（Ti O2）,barium titanate（Ba Ti O3）,silicon dioxide（SiO2）,etc.,can increase the dielectric constant of the material through interface polarization,but this will increase the material density and reduce the material density.Electrical breakdown performance,resulting in a reduction in energy density.The study found that the introduction of polar oligomers between the filler and the matrix can not only improve the electrical breakdown strength of the composite material by enhancing the interaction between the filler and the matrix,but also make use of the dual polarization of dipole polarization and interface polarization.The synergistic effect further increases the dielectric constant of the material.On the other hand,the polar oligomer itself can be used as a low-density lightweight dielectric filler to improve the dielectric and power generation properties of PMVS.Based on this,this paper designs a macromolecular coupling agent（MCA）modified silica/polymethylvinylsiloxane dielectric composite（MCA@SiO2/PMVS）and an organic lightweight filler/polyformaldehyde Based vinyl siloxane dielectric composite material（GBR-COOCH3/PMVS）,prepared long lifetimeand high enery harvesting performances dielectric elastomer composites,innovative work and results are as follows:（1）Preparation and properties of MCA@SiO2/PMVS dielectric composites: PMVS DE composites for DEG applications were designed and prepared by introducing high dielectric fillers and polar macromolecular coupling agents.A kind of silicon dioxide with low density and high polarization ability SiO2 was used as dielectric filler to effectively improve the dielectric constant of PMVS,and the ester group was grafted onto liquid butadiene rubber by mercapto-alkene click reaction to synthesize polar macromolecular coupling agent LBR-COOCH3（MCA）.Compared with the common small molecular coupling agent（SCA）modified SiO2（SCA@SiO2）/PMVS DE composite,the new MCA modified SiO2（MCA@SiO2）/PMVS DE composites have significantly increased cocrosslinking and chain entanglement,resulting in a significant increase in elongation at break and breakdown voltage under large strain（under 400%uniaxial strain）,and the interfacial interaction is further enhanced with the increase of MCA content.Therefore,As a result,MCA@SiO2/PMVS DEG exhibits an up-to-date highest energy density（92.2 m J/g）and power conversion efficiency（35.8%）among the previously reported DEG using unprestretched DE film,and its fatigue life reaches 141000 times,which is 3.9 times that of SCA@SiO2/PMVS DEG（36000 times）.Therefore,MCA@SiO2/PMVS DEG has the highest energy density in the whole life cycle（9710 J / kg）,which is4.8times and 2427 times higher than that of SCA@SiO2/PMVS DEG and commercial VHB DEG,respectively.and its fatigue life reached 141000 times,which was 3.9 times that of SCA@SiO2/PMVS DEG（36,000 times）.Therefore,MCA@SiO2/PMVS DEG has the highest full-life generating energy density（9710 J/g）,which is 4.8 times and 2427 times higher than that of SCA@SiO2/PMVS DEG and commercial VHB DEG,respectively.（2）Preparation and performance research of GBR-COOCH3/PMVS dielectric composites: Through the design and preparation of organic lightweight fillers,an all-organic PMVS-based DE composite material for DEG was designed and prepared.Firstly,LBR-COOCH3 is properly cross-linked to obtain GBR-COOCH3.Compared with high dielectric constant ceramic filler Ti O2,it can significantly improve the dielectric constant of PMVS through the dual polarization synergistic effect of dipole polarization and interface polarization,and at the same time make Composite materials have the characteristics of low modulus and high elasticity.In addition,co-crosslinking through residual double bonds improves the interfacial interaction and the interface defects can be reduced through its own tensile deformation,which improves the elongation at break and the electrical breakdown strength at large strain（under 400% uniaxial strain）of the DE film.Therefore,the energy density of GBR-COOCH3/PMVS DEG can reach 65.4 m J/g,the power conversion efficiency is as high as 38.4%,surpassing highest power conversion efficiency among uniaxially stretched DEGs reported in previous research.Its fatigue life reaches 30,000 times,which is 2.3 times that of Ti O2/PMVS DEG（13,000times）.GBR-COOCH3/PMVS DEG has the highest full-life generating energy density（943.2 J/g）,which is 2.2 times and 285.8 times that of Ti O2/PMVS DEG and commercial VHB DEG,respectively. |
