The present invention is a new class of terpolymers for use as high strain electrostrictive polymer films. More particularly, the invention is a class of electrostrictive terpolymers comprising vinylidene fluoride (VDF), trifluoroethylene (TrFE) and at least one monomer having at least one halogen atom side group. The monomer is preferably an ethylene-based monomer and preferably selected to favor gauche-type linkage along the polymer backbone. The halogen atom side group is preferably large enough to move or cause adjacent polymer chains to be farther apart from or away from each other than in the absence of such side group, but not so large that it would inhibit polymer crystallites from forming. The monomer is preferably a chloro-monomer such as chlorofluoroethylene (CFE). The chlorofluoroethylene (CFE) is preferably 1-chloro-2-fluoroethylene or 1-chloro-1-fluoroethylene. The chlorofluoroethylene (CFE) favors gauche-type linkage which favors high electrostrictive strains.