| abstract |
Solid star-branched block copolymers wherein each branch comprises at least two (2) alternating blocks bonded to each other, the free end of each branch being a block of at least one polymerized hydrocarbon conjugated diene (I), e.g. isoprene, containing at least 5 carbon atoms, with at least one carbon atom of each pair of residual double-bonded carbon atoms of polymerized diene (I) units being additionally single-bonded to two carbon atoms, or a copolymer of a least one diene (I) and at least one aryl-substituted olefin, e.g. styrene, the blocks adjacent to said polymerized diene (I) containing blocks constituting at least 50 wt. % of said copolymer and being a polymer of at least one hydrocarbon conjugated diene (B), e.g., 1,3-butadiene, which is different from diene (I) and contains at least four (4) carbons atoms, with each residual double-bonded carbon atom of polymerized conjugated diene (B) units being additionally bonded to a hydrogen atom. After the polymerization is completed, the block copolymer may be selectively hydrogenated, so that each (B) polymer block is hydrogenated to such an extent that it contains substantially none of the original ethylenic unsaturation, while each of the (I) polymer or copolymer blocks retains a sufficient amount of its original ethylenic unsaturation to cure (or vulcanize) the copolymer. |