Dielectric elastomers(DEs)have drawn much attention owing to their application prospects in artifi-cial muscles and soft robotics,it is still a big challenge to prepare DEs with high electromechanical performances.This work reports a highly stretchable poly(thioether)-b-polysiloxane-b-poly(thioether)tri-block copolymer based homogenous DEs with high electromechanical properties.The triblock copolymer(PSiPGE)was synthesized through the ring-opening polymerization(ROP)of phenyl glycidyl ether(PGE)and carbonyl sulfide(COS)catalyzed by silicon alkoxides.The dipoles(benzene rings)on the side groups of PSiPGE improved the dipole polarizations and the phase separation structure of this triblock copoly-mer enhanced the interfacial polarizations between poly(thioether)and polysiloxane,and thus improving the dielectric constant(s',up to 5.8).In addition,the PSiPGE exhibited low elastic modulus(Y,0.04 MPa),and thus possessed high electromechanical sensitivity(β,~145 MPa-1)which is much higher than that of most homogenous DEs.This work provides a new strategy to construct homogenous DEs with excellent electromechanical performances,leading to a greater application aspect in the actuated devices.