| 摘要 |
The invention relates to a star block copolymer of the formula [S1-S2-(B1/S3)-B2]m-X-[B2(B1/S3)-S2]n in which X represents a polyfunctional radical resulting from a coupling agent, m and n represent non-zero integers such that m+n is equal to 3 or 4, S1 and S2 each represent a block of a polymer containing at least one vinylaromatic monomer, B2 represents a block of a polymer containing at least one conjugated diene, (B1/S3) represents a block of a statistical copolymer containing at least one vinylaromatic monomer and at least one conjugated diene, 40 to 75% by weight of (B1/S3) consisting of resulting from vinylaromatic monomer, characterized in that the sum of the mass of the blocks B2 contains more than 40% by weight and less than 90% by weight of the total mass of the conjugated diene contained in the said star block copolymer. The invention also relates to the process for obtaining this copolymer. The compositions comprising this copolymer and crystal polystyrene have noteworthy mechanical properties and transparencies.
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