sulfur vulcanizable elastomers comprise interpolymers of a major proportion of one or more olefinic or haloolefinic hydrocarbons ; one or more esters of acrylic acid in which the acyclic or alicyclic radical moiety of the ester is free of olefinic unsaturation ; and a minor proportion , of about 0 . 10 to 10 mol percent of the total monomers present in the interpolymer , of an acyclic conjugated diolefin , prepared with a catalyst system comprising a lewis acid , a vanadium compound and a source of free - radicals such as an organic peroxide . the polymer chain consists of segments of alternating olefin and acrylic ester monomer units of variable length interconnected by randomly distributed diolefin units and the sum of the olefin and diolefin monomers in moles is substantially equal to the sum of the acrylic esters in moles present in the interpolymer . sulfur vulcanizates of these interpolymers exhibit high tensile , elongation and modulus and are amenable to blending with other elastomers , and compounding with fillers and reinforcing agents , or extension with process oils and plasticizers .