Retarded styrene anionic polymerization. 8. Influence of dialkylphenoxyaluminum on the reactivity of polystyryllithium species

This paper discusses the influence of dialkylphenoxyaluminum additives on the retardation of styrene polymerization initiated by alkyllithium. Data are compared with results obtained with trialkylaluminum. Similar decreases of the propagation rate can be achieved with both types of compounds. Although with R3Al additives (i-Bu3Al, Et3Al, Me3Al), reactivity extinction appears with the formation of inactive 1:1 (Al/Li) mixed complexes, at a ratio of [Al]/[Li]=1, in the presence of diisobutyl-2,6-di-tert-butyl-4-methyl-phenoxyaluminum, extinction occurs at a ratio of [Al]/[Li]=0.5. This was correlated to an irreversible ligand exchange between the polystyryllithium and the phenoxyaluminum derivative, as proved by the formation of the corresponding lithium phenoxide, prior to formation of a 1:1 complex.