Copolymerization of a 1,3-cyclodiene and a linear conjugated diene

A method comprising:

• copolymerizing a 1,3-cyclodiene comonomer and a linear conjugated diene comonomer in the presence of a catalyst formed from a mixture comprising
• (a) a triorganoaluminum compound represented by the general formula R.sub.3 "Al wherein R" is a hydrocarbon radical containing from 1 to 20 carbon atoms selected from the group consisting of alkyl, cycloalkyl, aryl, alkaryl, aralkyl, and mixtures thereof;
• (b) a nickel (II) compound;
• and
• (c) a Friedel-Crafts type Lewis acid cocatalyst wherein the amount of the triorganoaluminum compound is in the range of from about 0.5 to 30 moles per mole of the nickel (II) compound, the amount of the Friedel-Crafts type cocatalyst is in the range of from about 0.5 to 30 moles per mole of the nickel (II) compound, and the amount of nickel (II) compound is in the range of from about 0.05 to 50 millimoles per hundred grams of total comonomer,
• wherein the linear conjugated diene comonomer and the Friedel-Crafts type cocatalysts are added to a mixture comprising the nickel (II) compound and the triorganoaluminum compound wherein the mixture is aged from about 2 minutes to 5 hours, at a temperature in the range of from about 0.degree. to 100.degree. C. prior to adding the linear conjugated diene comonomer and the Friedel-Crafts type cocatalyst to said mixture, and said 1,3-cyclodiene is added prior to, during or after formation of the reduced nickel (II) compound by aging the mixture, but the reduced nickel II compound is contacted with the 1,3-cyclodiene prior to contacting the conjugated diene comonomer.