In summary there are presented some new data on the initiation step for poly-(butadiene) polymerization with the AlEt3-Ni-BF3 catalyst which describe what appears to be a “settling down” period of newborn chains at the π-bonded nickel catalyst site. This leads to a segment of higher trans content at the end of each high cis-1,4-poly(butadiene) chain. Comparisons between nickel and cobalt catalysts seem to point up their differences rather than their similarities. We have described the role of water in effectively changing the identity of the aluminum alkyl which in turn has a marked effect on the polymerization rate, on the polymer molecular weight and the extent of crosslinking.

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