Thermally expanded graphene nanoplates/polydimethylsiloxane composites with high dielectric constant, low dielectric loss and improved actuated strain

Abstract

Abstract Thermally expanded graphene nanoplates (TGNPs) were introduced into polydimethylsiloxane (PDMS) matrix by using solution mixing method to obtain TGNPs/PDMS dielectric composites with high dielectric constant (k), low dielectric loss and large actuated strain. The results indicated that the k at 103 Hz was obviously increased from 3.1 for pure PDMS to 18.3 and 89.5 for the composite with 1.6 wt% and 2.0 wt% TGNPs, respectively. Meanwhile, the volume resistivity of all the composites was larger than 109 Ω cm, indicating a low direct current conductance. As a result, the dielectric loss at 103 Hz retained a low value for all the composites. In addition, a significant increase in actuated strain was obtained from 1.4% for pure PDMS to 3.6% with the addition of 2.0 wt% TGNPs under a low electric field (15 V/μm). The mechanism for the largely improved dielectric properties was carefully discussed based on the uniform dispersion of TGNPs in PDMS matrix, the gradual formation of many parallel or serial micro-capacitor structures (low direct current conductance) with the content of TGNPs increasing, and the remained oxygenic groups coated on TGNPs after high temperature thermal exfoliation. Our work provided a simple, low-cost and effective method to prepare high performance dielectric elastomer (DE), facilitating the wide application of DE composites, especially in the biological and medical fields such as biosensors, artificial muscles, and prosthetics.