Dehydrogenation of poly(1,3-cyclohexadiene)–polystyrene binary block copolymers

The dehydrogenation of poly(1,3-cyclohexadiene)–polystyrene binary block copolymers obtained by anionic copolymerization with alkyllithium/amine systems was investigated for the first time. The dehydrogenation of the poly(1,3-cyclohexadiene) block, which was composed of 1,2-cyclohexadiene (1,2-CHD) and 1,4-cyclohexadiene (1,4-CHD) units, was strongly affected by the polymer chain structure. The existence of 1,2-CHD units prevented the dehydrogenation of the poly(1,3-cyclohexadiene) block in the binary block copolymer. The rate of dehydrogenation was fast on a long sequence of 1,4-CHD units, whereas it was relatively slow for 1,2-CHD/1,4-CHD (≈1/1) unit sequences. The bonding of the polystyrene block to the polymer chain effectively improved not only the rate of dehydrogenation of a long sequence of 1,4-CHD units but also that of the polymer chain with a high content of 1,2-CHD units. The dehydrogenation of a poly(1,3-cyclohexadiene) block containing a small number of 1,2-CHD units progressed via step-by-step reactions. The dehydrogenation of a long sequence of 1,4-CHD units proceeded as the first step. Subsequently, in the second step, the 1,2-CHD/1,4-CHD (≈1/1) unit sequences remaining in the polymer chain were dehydrogenated. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3526–3537, 2006