Preparation And Properties Of High Dielectric Constant Acrylate Elastomer Based Composites

Acted as one kind of electroactive polymers,dielectric elastomers are capable of altering their volume or size once applied to electric field,which realizes the conversion from electric energy to mechanical energy and the transform is reversible.Dielectric elastomers hold the broad application potential in in numerous cutting-edge fields such as sensors,actuators,energy harvesters and biomedicine on account of their fast response(<1ms)and high energy density.To acquire large deformation of dielectric elastomers,it is feasible to increase their dielectric constant or decrease elastic modulus in the case of low electric field.Consequently,this work aimed at increasing the dielectric constant and simultaneously maintaining low elastic modulus.The study was based on butyl acrylate,styrene and hydroxyethyl acrylate to synthetize acrylate elastomer(AR)with free radical polymerization.Subsequently,two kinds of AR based nanocomposites with high dielectric constant and low dielectric loss were fabricated with two novel graphene hybrids.Polysiloxane modified polyaniline(HBSiPA)was synthetized with the opening ring reaction of ternary polymerization polyaniline(d-PANI)and hyperbranched polysiloxane(HBSi)fabricated by hydrolysis reaction ofγ-(2,3-epoxypropoxy)propyl trimethoxysilane.~1H-NMR and FT-IR proved that AR was synthesized successfully.In addition,the solubility and thermal stability of HBSiPA were superior to that of d-PANI.Then,the first novel graphene hybrid HBSiPA–TrGO was fabricated by hybridization of HBSiPA and thermally reduced graphene oxide(TrGO).IL,sulfonic propyl imidazolium ionic liquid,was synthesized by a two-step method composed of quaternary amination reaction and acidification reaction.Subsequently,the second unique graphene hybrid PILs–CrGO was fabricated by in situ chemical polymerization of ILs on the surface of chemically reduced graphene oxide(CrGO).The strongπ–πinteraction between HBSiPA and TrGO along with between PILs and CrGO was confirmed by XPS,FT-IR,UV-vis and Raman characterization techniques.Besides,the results of XRD,SEM,TEM and AFM confirmed that graphene sheets were exfoliated into few or single layer with the introduction of HBSiPA or PILs,which hindered the agglomeration and stacking of graphene sheets effectively.Different contents of the two kinds of graphene hybrids worked as conductive fillers were added into AR to fabricate acrylate elastomer based nanocomposites and simultaneously fabricate composites with graphene as filler.SEM and XRD analysis suggested that it was beneficial to the dispersion of graphene with the introduction of HBSiPA or PILs.DSC and TGA analysis indicated that unique graphene hybrids enhanced the thermal stability of AR.Moreover,based on percolation theory,percolation threshold values of HBSiPA–TrGO/AR and PILs–CrGO/AR composites were 2.42 vol%and 1.71 vol%,respectively.The dielectric constant of 2.83 vol%HBSiPA-TrGO/AR and 1.69 vol%PILs-CrGO/AR nanocomposites were 355 and 640,respectively;the dielectric loss of them were 0.37and 0.34,respectively.The dielectric property of the two kinds of nanocomposites was better than that of graphene/AR composites.Analog circuit fitting and analysis demonstrated that the improvement of dielectric property was attributed to the formation of the graphene hybrid conductive paths and the enhanced MWS polarization effect.In addition,the elastic modulus of the nanocomposites was lower than 5 MPa and still was suitable for manufacturing sensors and actuators.