Ultrasoft-yet-strong pentablock copolymer as dielectric elastomer highly responsive to low voltages

Electrically active dielectric elastomer has been a leading technology for artificial muscle. It remains a great challenge to significantly reduce the actuation voltage down to far lower than 1 kV. Here, we report that well-designed pentablock copolymer could be an excellent strategy to address the challenge. Particularly, pentablock copolymer (SEHAS)2 (S for polystyrene, EHA for poly(2-ethylhexyl acrylate)) with suitable composition exhibits ultrasoft-yet-strong property, which is rarely observed in an elastomer. The sparse entanglements together with relatively high chain-loop concentration in the EHA phase make the material significantly softer than most elastomers. The middle block of polystyrene reinforces the hard nanodomains to provide the high tensile strength. The ultrasoft-yet-strong property together with high extensibility and good processability allows us to conveniently fabricate an ultrathin actuator, which is highly responsive to low voltage (area strain 93% at 680 V and 30% at 240 V).