| abstract |
Conjugated dienes, in particular 1,3-conjugated dienes, can be polymerized or copolymerized using the catalyst system of this invention to polymers wherein the amount of 1,2-structure contained in the polymer is increased, and polymers can be prepared containing varying amounts of 1,2-structure as desired. Such desirable results can be obtained in accordance with the process of the present invention for polymerizing conjugated diene monomers which comprises the use of a catalyst system which comprises (a) at least one anionic initiator based on lithium, and (b) a modifier composition comprising at least one cyclic acetal of a glyoxal. <IMAGE> wherein R and R' are each independently hydrogen, alkyl or aryl groups, and each A is independently an alkylene or an oxyalkylene group. In another embodiment, the catalyst system also contains at least one co-initiator selected from the group consisting of organomagnesium compounds, organoaluminum compounds, or mixtures thereof. |