Soft silicone elastomers exhibiting large actuation strains

Poly(dimethyl-co-methylvinyl)siloxane-α,ω-diols with 1.5, 5.5, and 8.5 mol% vinyl group contents, respectively, are obtained via an environmental friendly synthesis and used as platforms for further chemical modification via a green process. This chemical modification consists of UV-activated thiol-ene addition of 3-chloro-1-propanethiol to the vinyl groups, as proven by NMR analysis. Cross-linking with tetraethyl orthosilicate (in excess) of such modified polymers leads to dielectric elastomers with higher values of dielectric permittivity than those of non-chemically modified vinyl copolymers cross-linked under similar conditions. In addition, at high chloropropyl content, there is a significant decrease in Young's modulus, attributed to the plasticizing effect of the alkyl segment of the attached chloropropyl, and only a slight increase in breakdown strength is observed. All these changes induced by the chloropropyl group act synergistically in favor of the electromechanical performances of the resulting elastomers that exhibit large out-of-plane actuation strains of 53% and 61% for polar contents of 5.5 and 8.5 mol%, respectively, at an applied electric field of 40 V/μm. These are to the best of our knowledge the largest out-of-plane actuation strains from silicone elastomers reported in literature.