POLYMERIZATION OF 1,3-DIENES WITH THE SOLUBLE CATALYST SYSTEM METHYLALUMINOXANES-[CPTICL3] - INFLUENCE OF MONOMER STRUCTURE ON POLYMERIZATION STEREOSPECIFICITY

In combination with methylaluminoxanes, [CpTiCl3] gives a soluble catalyst that has remarkable activity for the polymerization of conjugated dialkenes. Polymers with a cis-1,4 structure (> 98%) have been obtained from 2,3-dimethylbutadiene, 2-methylpentadiene and (Z)-pentadiene. Crystalline polymers with a 1,2 syndiotactic structure have been obtained from 4-methylpentadiene. Other monomers give amorphous polymers with a mixed 1,4/1,2 structure. An interpretation of the mechanism of formation of the polymers is proposed. The mode of orientation of the incoming monomer with respect to the last polymerized unit and the different reactivity of the butenyl groups derived from the various monomers are believed to be the main factors that determine polymer structure.