Block copolymers of α‐olefins prepared from macromolecules with long chain lifetimes

Abstract

AbstractIt has been shown that certain Ziegler‐type catalysts, i.e., mixtures of TiCl4 with lithiumaluminium alkyls or VOCl3 with aluminum chloroalkyls, produce “living” macromolecules having lifetimes of the order of several days or more in the homo‐ and copolymerization of α‐olefins. The long‐lived macromolecules made it possible to prepare stereoblock copolymers of α‐olefins consisting of blocks of random copolymers alternating with blocks of homopolymers with a certain steric isometry and with a wide range of physical properties. Some of the relationships existing between the molecular structure and the physical properties of these model block copolymers have been studied and compared with random copolymers and homopolymers of α‐olefins. Crystallizable elastomers composed of amorphous random copolymer blocks of ethylene and propylene or ethylene and butene‐1, alternating with homopolymer blocks of ethylene, propylene, or butene‐1 are discussed. In particular, the homogeneity of the products, the stress–elongation behavior, the x‐ray diffraction patterns in the unstretched and stretched states, and the physical properties of the reinforced and vulcanized products of the crystallizable stereoblock rubbery copolymers are presented.