Preparation And Dielectric Properties Of Polysiloxane Graft-Modified By Ugi-4Cr

Dielectric elastomers are typical electric field-type electroactive polymers that can realize electrical and mechanical energy conversion.The two major applications of dielectric elastomers are actuators(DEA)and generators(DEG),and they can also be used as artificial muscle materials.They have been widely concerned and studied in the field of energy conversion.In this paper,silicone rubber,which is one of the ideal materials for dielectric elastomers,is used as the research object.Condensation cross-linking,UV-induced thiol-ene click reaction cross-linking,hydrosilylation cross-linking,peroxide-induced thermal cross-linking and radiation cross-linking were compared.Dielectric permittivity,dielectric loss and electrical conductivity were tested using a broadband dielectric impedance spectrometer,and breakdown strength was tested using an electrical breakdown tester.The unmodified silicone rubber has a relatively close dielectric permittivity,while the addition-crosslinked silicone rubber has lower loss,conductivity and higher breakdown strength.The Yong’s modulus of the silicone rubber prepared by room temperature crosslinking is lower therefore more suitable as an actuators material.Using thiol-ene click reaction and Ugi-4CR to introduce diamide structure and various functional groups on polysiloxane side groups,four polar polysiloxanes were synthesized.Their structures were characterized by NMR and FT-IR,and glass transition temperatures(T_g)were measured by DSC.The T_g was greatly increased,and the grafting rate was controlled to keep it below0°C.Using different ratios of unmodified polysiloxane and polysiloxane with polar side groups,a series of high dielectric permittivity and low modulus elastomer films were obtained by UV-induced crosslinking of thiol-ene click reactions.The crosslinking density was calculated by swelling experiments,the dielectric properties and mechanical properties of the elastomer films were compared with unmodified ones,and the storage modulus,loss modulus and loss angle at 1-10Hz were characterized by DMA,and finally tested their lateral actuation strain.The test of mechanical properties shows that the elastomers have a very low modulus(less than 0.5MPa),and elasticity is slightly reduced;the test of dielectric properties shows that the elastomers have a higher dielectric permittivity(more than 3)than the unmodified ones.The increase in dielectric permittivity and the decrease in modulus enable the elastomers to obtain a maximum actuated strain of 8.9%at a field strength of 23k V/mm.