Reaction rate and molecular weight of product as a function of monomer concentration in propylene polymerization on the VCl₃-Al(i-Bu)₃ system

Summary

• 1. A study has been made of the polymerization rate of propylene on VCl₃-Al(i-Bu)₃ and of the molecular weight of the product as a function of propylene concentration in the liquid phase at 30, 45, and 60°.

• 2. The reaction rate at quite high monomer concentrations is proportional to the first power of the monomer concentration, while at low concentrations, the order of the reactions in the monomer is observed to increase (to the second in the limit).

• 3. The degree of polymerization increases with increase in propylene concentration at low monomer concentrations, and remains practically constant for quite high monomer concentrations.

• 4. At least part of the acts leading to stoppage of polymer chain growth are chain rupture acts, after which the active centers, regenerated so as to be converted into growth centers, will go through the initiating stage with a rate constant k_i considerably less (three or four orders of magnitude) than the rate constant for the chain growth act, k_g.

• 5. Values are found for the activation energy of the various stages of the reaction.