Preparation And Properties Of Itaconate-Based Dielectric Elastomer

Dielectric elastomer(DE)is a new type of electroactive polymer that can produce reversible deformation under the action of an external electric field and convert electrical energy into mechanical energy,which has potential applications value in intelligent robotics,biomedicine and aerospace.Conventional dielectric elastomer materials often require large actuated voltages to generate large actuated strains due to their low dielectric constants,limiting their further applications.Therefore,it is necessary to develop dielectric elastomers to generate large actuated strains at lower field strengths.Itaconic acid is a compound of biomass origin and contains two active carboxyl groups,it is easy to esterify with alcohol.Di-n-hexyl itaconate(DHeI),obtained by esterification of itaconic acid with hexanol,includes two polar ester groups and can effectively improve the dielectric constant of dielectric elastomer materials.So a series of intrinsic biomass-based dielectric elastomer materials were synthesized by free radical polymerization using DHeI and butyl acrylate(BA)as the main monomers,and the electrical actuated properties were investigated systematically.The main research contents and results are as follows:First,DHeI was synthesized by esterification reaction using itaconic acid(IA)and n-hexanol as raw materials.Then,a series of poly(di-n-hexyl itaconate-butyl acrylate-glycidyl methacrylate)(P(DHeI-BA-GMA))self-crosslinked dielectric elastomers were synthesized by free radical polymerization using DHeI and BA as the main monomers and glycidyl methacrylate(GMA)as the crosslinked functional monomer.And the effect of monomer ratio on the electric actuated properties was investigated.It was shown that the elastic modulus of P(DHeI-BAGMA)elastomer decreased from 0.28 MPa to 0.18 MPa and the dielectric constant(1 kHz)increased from 6.4 to 8.9 with the increase of DHeI content.When the molar ratio of DHeI to BA was 4:6,the P(DHeI-BA-GMA)-4:6 self-crosslinked elastomer had the best electric actuated performance,exhibiting an electrically driven strain of 58.90%at an electric field strength of 37.34 kV/mm.Secondly,a series of P(DHeI-BA-GMA)self-crosslinked dielectric elastomers with different degrees of cross-linking were synthesized by varying the amount of GMA,and the effect of GMA content on the electrical actuated properties of P(DHeI-BA-GMA)self-crosslinked dielectric elastomers was further investigated.It showed that the tensile strength of P(DHeI-B A-GMA)elastomers was effectively improved with the increase of GMA content,and the breakdown strength was also slightly increased,but the corresponding elastic modulus also increased significantly.Therefore,the maximum electrically actuated strain of P(DHeI-BA-GMA)self-crosslinked elastomer decreased minor with the increase of GMA content.The P(DHeI-BA-GMA)-1%self-crosslinked elastomer exhibited the best electrically actuated performance when the content of GMA was 1%.Finally,a series of P(DHeI-BA-GMA)dielectric elastomers with different crosslinked network structures were prepared by modifying P(DHeI-BA-GMA)polymers with hexanediamine(HMD),polyetheramine D400(D400)and polyetheramine T403(T403),respectively.And the effect of crosslinker types on the electrical actuated properties of P(DHeI-BA-GMA)was investigated.It showed that the elastic modulus of P(DHeI-BA-GMA)elastomers modified by external crosslinking was significantly reduced and the dielectric constant was increased,comparing to the self-crosslinked P(DHeI-BA-GMA)dielectric elastomers.Among them,D400 modified P(DHeI-BA-GMA)elastomer exhibited the lowest elastic modulus of 0.11 MPa;the highest dielectric constant(1 kHz)of 10.5;and the best electric driving performance.It showed an electrically actuated strain of 41.01%at a low field strength of 21.78 kV/mm.