Course of the terpolymerization of ethylene,propylene, and dicyclopentadiene. II. Two-step addition of dicyclopentadiene

Terpolymerizations of ethylene, propylene, and dicyclopentadiene were carried out in which the dicyclopentadiene was added to the reaction system in two equal portions at the beginning and midpoint of each run, while the monoolefins were added continuously. In the resultant elastomers, unsaturation remains much more constant throughout the course of the polymerization than for terpolymers obtained when all dicyclopentadiene is added at the start of the reaction. Yield and molecular weight of the terpolymers produced by either technique are quite comparable, however. With VCl₄ catalyst (with Al₂Et₃Cl₃ cocatalyst) in heptane solvent, the two-step addition of the diene gave terpolymers with little gel, in contrast to the high gel in terpolymers formed with the single initial addition of the diene. This system also produced terpolymer with the highest final unsaturation and molecular weight. Catalysts of VCl₄, VOCl₃, or V(C₅H₇O₂)₃ in benzene gave terpolymers of moderate unsaturations and molecular weights.