Poly(4‐methyl‐1‐pentene) and some soluble crystalline copolymers

Poly(4‐methyl‐1‐pentene) has been prepared by polymerizing the monomer over a catalyst made from titanium tetrachloride and lithium aluminum tetradecyl. The molecular weight of the crystalline polymer was invariably too high for fiber preparation, even when polymerization variables were varied drastically, so a technique for thermal cracking was developed. By heating grease‐free, crystalline poly(4‐methyl‐1‐pentene) in a vacuum at about 280°, it was possible to lower smoothly the molecular weight of the polymer to any desired value, without undesirable crosslinking or by‐product formation. The polymer was melt‐spun by conventional techniques to highly oriented, tough fibers. Copolymerization of 10–25% 1‐hexene and other linear 1‐olefins with 4‐methyl‐1‐pentene gives products which are still high‐melting, but which are readily soluble in such solvents as cyclohexane or chloroform, in contrast to the homopolymer which is only slightly soluble. Polymerization in solvents for the copolymer gave solutions which were converted to fibers and film without intermediate isolation of polymer or removal of the catalyst. An interesting terpolymer in which divinylbenzene was the third component was found to be initially soluble, but was readily crosslinked at elevated temperature.