STRUCTURE OF CIS 1,4-POLYBUTADIENES AND 1 ,2-POLYBUTADIENES SYNTHESIZED WITH CATALYTIC-SYSTEMS DERIVED FROM TRANSITION-METAL COMPOUNDS AND ALUMINOXANES

The structure, phase composition, and temperature behavior of cis-1,4- and 1,2-polybutadienes synthesized with the new catalytic systems con sisting of a transition-metal compound and methyl-, ethyl, or isobutyl aluminoxane were studied by IR and C-13 NMR spectroscopy, DSC, and X-r ay diffraction analysis. Cobalt diethyldithiocarbamate, cobalt salt of 2-mercaptobenzothiazole, titanium tetrabutoxide, and vanadium alkoxid es were used as transition-metal compounds. The catalytic systems deri ved from methylaluminoxane make it possible to prepare polymers on the basis of 1,4-butadiene. It was found that the replacement of methylal uminoxane by ethyl-or isobutylaluminoxane gives rise to 1,2-polybutadi ene. It is suggested that, in the catalytic complex containing aluminu m compound with methyl groups, coordinated diene is predominantly adde d to the terminal carbon of the polymer chain, producing 1,4-units. Wh en aluminum is linked to bulkier alkyl groups, coordinated diene is ma inly added to the C(3) atom of a polymer chain, and, as a result, 1,2- units are formed. cis-1,4-PB samples synthesized at high temperatures show a tendency toward supercooling. At low temperatures, their phase composition markedly depends on temperature and the rate of cooling. T he phase diagram of cis-1,4-PB in the coordinates temperature-intrinsi c viscosity was constructed.