1,3-cyclohexadiene polymers. 1. Anionic polymerization

The anionic polymerization of 1,3-cyclohexadiene (1,3-CHD) using various in itiating systems and with or without additives was studied. In contrast to the situation with linear conjugated dienes, common anionic initiators in t he absence of additives fail to produce poly(1,3-cyclohexadiene) (PCHD) wit h controlled molecular weight (MW) and narrow molecular weight distribution (MWD) because of side reactions. However, certain additives change the nat ure of the polymerization dramatically. Monodentate additives do not yield controlled polymerization, while some polydentate additives, such as N,N,N' ,N'-tetramethylethylenediamine (TMEDA), 1,2-dimethoxyethane (DME), and 1,4- diazabicyclo[2.2.2]octane (DABCO), are effective in minimizing side reactio ns, if combined with the suitable butyllithium isomer. For example, the syn thesis of PCHD samples with narrow MWD and good MW control is possible usin g the n-BuLi/DME/0 degreesC or sec-BuLi/DABCO/20 degreesC in benzene. The " living" character of these polymerizations is discussed.