Triisobutyl aluminium．titanium tetrachloride can induce cis-1

4-polymerization of butadiene when a certain amount of iodine is added．The effects of molar ratio of triisobutyl aluminium to titanium tetrachloride

molar ratio of iodine to titanium tetra-chloride，concentration of titanium tetrachloride and polymerization temperature on con-version，molecular weight，and microstructure of the polymer have been studied． It is shown that iodine reacts with triisobutyl aluminium to form diisobutyl aluminium iodide which is one of the real components of the catalyst．If diethylaluminium iodide is used instead of iodine，cis-1，4-polymerization can likewise be induced．Wjthout triisobutyl aluminium．polymerization does not occur．Experiments indicate that triisobutyl alumi-nium functions as a reducing agent which reduces titanium from tetravalent state to divalent state．If tetrabutyl titanate instead of titanium tetrachloride is used in corn-bination with iodine and triisobutyl aluminium

cis-1，4-polymerization of butadiene also occurs.