1,3-Cyclohexadiene Polymers. 3. Synthesis and Characterization of Poly(1,3-cyclohexadiene-block-styrene)

The synthesis of block copolymers of 1,3-cyclohexadiene (1,3-CHD) and styrene under various conditions is reported. sec -Butyllithium alone can initiate the polymerization of 1,3-CHD but does not yield a living process due to chain transfer and termination reactions. However, certain additives such as tetramethylethylenediamine, dimethoxyethane, and 1,4-diazabicyclo[2.2.2]octane, combined with the suitable butyllithium isomer, can be used to improve control of the polymerization of 1,3-CHD. Using these initiator systems, well-defined poly(styrene- block -1,3-cyclohexadiene)s with a wide range of compositions were synthesized and thoroughly characterized. In addition, the rate of crossover reactions during block copolymer formation and the “random” copolymerization of 1,3-CHD and styrene were investigated.