Silicone elastomers with covalently incorporated aromatic voltage stabilisers

When optimising dielectric elastomers (DEs) a conflict exists, namely that for large achievable actuationstrains softness is required, but with increased softness electrical breakdown strength decreases. Herein,soft dielectric silicone elastomers with increased electrical breakdown strength, due to the incorporationof an aromatic voltage stabiliser, were prepared by cross-linking synthesised polydimethylsiloxane–polyphenylmethylsiloxane (PDMS–PPMS) copolymers. PPMS possesses voltage stabilisation capabilitiesbut is immiscible in PDMS, and thus the copolymerisation of the two components was necessary forhomogeneity. Concentrations of the voltage stabiliser were varied by changing the molecular weights ofthe PPMS in the copolymer. The developed elastomers were inherently soft with enhanced electricalbreakdown strengths, due to delocalisedp-electrons of the aromatic constituent. An optimumconcentration was found for the voltage stabilisation effect. The relative permittivities of thePDMS–PPMS elastomers varied from 3.4 to 3.9 and therefore were also improved from pure PDMSelastomers. The elastomers were furthermore non-conductive and possessed low dielectric losses.These properties are evaluated as favourable for soft actuation