Piloting of anionic polymerization of styrene in tetrahydrofuran

Anionic polymerization of styrene in THF with n-butyllithium /alpha-methylstyrene initiator is described as a first step in preparation of a styrenic block copolymer. In order to suppress rapid decay of living alpha-methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at -20(plus/minus5) deg C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modeling of styrene propagation reaction all key process parameters were defined for 1-L, 38-L, and 189-L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well-defined polymers up to Mn 22 000 via the living polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30).