Hydrogen effect on the molecular weight distribution of polymers obtained by polymerization of ethylene and α‐olefins over supported titanium‐magnesium catalysts

Abstract

AbstractComparative data on the molecular weight distribution of polymers obtained by polymerization of ethylene, propylene and 1‐hexene, and copolymerization of ethylene with α‐olefins over the titanium‐magnesium catalysts (TMC) in the absence and presence of hydrogen are presented. In contrast to the ethylene polymerization, in the cases of propylene and 1‐hexene polymerization and copolymerization of ethylene with α‐olefins, the hydrogen addition is characterized by noticeable narrowing of the molecular weight distribution (MWD) due to lower contribution of the MWD component with high molecular weight. This result is an evidence of the increased reactivity of TMC active sites producing high molecular weight poly‐α‐olefins and copolymers of ethylene with α‐olefins in the chain transfer reaction with hydrogen. It is suggested that the increased reactivity of these sites in the transfer reaction with hydrogen appears after the 2,1‐addition of α‐olefin to the growing polymer chain.