Importance

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Abstract

The invention is a process for the preparation of a block copolymer which corresponds to the formula ABA wherein A comprises units derived from one or more monoalkenyl arenes; and B comprises units derived from one or more conjugated dienes and the residuum of a difunctional initiator; wherein the process comprises: I) contacting (a) a difunctional initiator capable of initiating the polymerization of a compound containing a double bond with (b) a portion of conjugated diene in a portion of hydrocarbon solvent under conditions such that the conjugated diene polymerizes to a degree of polymerization of 30 or greater; II) contacting with the polymerization mixture of I additional conjugated diene and hydrocarbon solvent under conditions such that the added conjugated diene polymerizes; and III) contacting with the polymerization mixture of II a monoalkenyl arene to prepare a block copolymer having a number average molecular weight of about 31,500 to about 400,000 and an average weight percent of monoalkenyl arenes contained in the block copolymer of from about 5 percent to about 50 weight percent under conditions such that the monoalkenyl arene polymerizes. In another embodiment, the invention relates to the polymers prepared from this process. Such products demonstrate high tensile strength, a low polydispersity index and do not require the use of a co-initiator to achieve such properties.

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First Claim