| 摘要 |
A process for preparing a radial polymer comprising at least 3 polymeric arms and a central core comprising a polymerized di- or polyfunctional monomer, said process comprising the steps,(a) polymerizing at an elevated temperature, a charge comprising at least one free radical-polymerizable monomer to prepare a stabilized active polymer block (A) using a free radical polymerization process,wherein a stable free radical agent is employed during the polymerization, thereby preserving the stabilized active polymerization site at the terminus of the polymer; optionally(b) adding at least one additional free radical-polymerizable monomer, at least one of which is different from the monomers making up the first charge of monomers, to the stabilized active polymer block (A); and further reacting the mixture using a free radical process to effect copolymerization of said monomers, thereby preparing an A-B block copolymer having a stabilized active polymerization site at the terminus of the polymer; then(c) adding at least one coupling agent comprising a polyfunctional monomer and reacting the stabilized active polymers from (a) or (b) with a coupling agent to form a radial polymer.The present invention also relates to polymers, including block copolymers prepared by the above process, additive concentrates for preparing lubricating oil compositions and lubricating oil compositions. In other embodiments, the present invention relates to block copolymers having more than two blocks.
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