Heterophase polymerization of isobutene with aluminum chloride catalyst solutions

The low temperature polymerization of isobutene with AlCl3 in methyl chloride solutions has been investigated. In a series of experiments the degree of polymerization of poly(isobutene)as a function of monomer concentration has been determined. It was found that increasing amounts of methyl chloride causes a marked increase in molecular weight until a sharp maximum is reached at about 0.10 mole fraction isobutene. Further dilution causes a precipitous drop in the molecular weights. It has been shown that increase in dielectric constant does not account for the rise in degree of polymerization. The log of degree of polymerization was found to be inversely proportional to the log of catalyst concentration between about 10−3–10−2 wt.‐% (7.53 × 10−5–10−4 mole liter−1)AlCl3 on monomer. At higher catalyst concentrations the degree of polymerization becomes concentration independent. This was true for methyl isobutene–chloride systems containing 1.0, 0.65, and 0.25 mole fraction of monomer. The product degree of polymerization times monomer concentration falls on the same curve.