Diene polymerizations with lanthanide coordination catalysts. II. The effects of catalytic system component types and polymerization conditions on molecular characteristics of 1,4- cis-Polybutadienes

Abstract

Molecular inhomogeneity has been investigated for 1,4- cis-polybutadienes obtained with a lanthanide- containing catalytic system; some kinetic parameters have been estimated for polymerizations. Gel-permeation chromatography was chosen as the main method to find out the average molecular weights (MW) and molecular weight distributions (MWD). The catalyst composition has been shown to effect MW and MWD. The molecular characteristics are determined by both the catalyst composition and the polymerization conditions (reagent concentration, temperature). The broad MWD is considered a peculiarity of butadienes prepared with lanthanide- containing catalysts. The data obtained lead to the assumption that the distribution of the polymerization centres by reactivity is responsible for the broad MWD of the polybutadienes formed.