Nonconjugated conductive polymers, which are all polymers that have a ratio of double bonds to total bonds of less than ½ are doped with iodine to produce compositions with unexpected characteristics in this invention. The mechanical and elastomeric properties of a nonconjugated polymer can be enhanced by doping the polymer with an electron acceptor such as iodine, in order to cure the polymer. Among the nonconjugated polymers are the cis-1,4-polyisoprene, cis-1,4 polybutadiene, styrene-butadiene copolymers (SBR), ethylene-propylene-diene monomer and poly (β-pinene). A heated mixture of iodine and sulfur produces a faster rate of vulcanization of rubber than using sulfur alone.