| abstract |
There are disclosed novel, solid, elastomeric block copolymers having excellent oxidative and thermal stability, wherein the terminal blocks are each a polymer (D polymer) of at least one conjugated diene D, which is a hydrocarbon containing a 1,3-conjugated diene structure wherein the 2 and 3 carbon atoms are each additionally bonded to a hydrocarbyl side group, e.g., 2,3-dimethyl-1,3-butadiene, with a preponderance of polymerized D units being 1,4 units; and at least one interior block is a hydrogenated polymer (I polymer) of at least one conjugated diene I which is a hydrocarbon containing a 1,3-conjugated diene structure wherein one of the 2- and 3-carbon atoms is additionally bonded to a hydrocarbyl side group and the other is additionally bonded to a hydrogen atom, e.g. isoprene. The block copolymers may be prepared by selectively hydrogenating substantially all the I polymer units of a precursor block copolymer with a sufficient number of D units in the D polymer blocks retaining their unsaturation on selective hydrogenation to enable the vulcanization of the block copolymer. |