Properties of isotactic, atactic, and stereoblock homopolymers, random and block copolymers of α‐olefins

Abstract

Abstract The study of several methods of controlling the molecular weight in the stereospecific polymerization of α‐olefins leads us to a better understanding of the neture of coordinated ionic catalysis. Some physical and chemical factors that influence the steric composition of polymers have been examined and a kinetic interpretation of stereoblock Polymers is proposed. A continuous variation of physical properties, particularly of crystallinity, melting point, and densities, and mechanical properties is observed as functions of the length of the steically homogeneous section in stereoblock polymer. This length is related to the number of steric irregularities of the chain. A new method to prepare block copolymers of different monomers is described; these copolymer show evidence of crystallinity due to long sequences of the same monomeric units, but properties different from those of physical mixtures of homopolymer and from those of random copolymer. The production of random copolymer has been examined, particularly of amorphous ethylene‐propylene copolymer having interesting elastomeric properties.