| abstract |
A process is provided for the preparation of tapered copolymers by the nonaqueous dispersion polymerization of a mixture of 30 to 70% by weight of a conjugated diolefin monomer, preferably butadiene, and 30 to 70% by weight of a vinyl substituted aromatic monomer, preferably styrene, in a liquid hydrocarbon dispersion medium with an anionic initiator catalyst system in the presence of a block copolymeric dispersing agent. At least one block of the dispersing agent is prepared prior to the dispersion polymerization reaction and at least one block of the dispersing agent is prepared in situ during the dispersion copolymerization. The block of the dispersing agent that is prepared in situ has the polymer structure of the tapered copolymer. |