Retarded styrene anionic polymerization, 7. Influence of mono- and diphenoxymagnesium derivatives on both the reactivity and thermal stability of polystyryllithium species at high temperature†

The influence of monophenoxymagnesium (2,6- di-tert-butyl-4-methylphenoxybutylmagnesium, BuMgOBT) and diphenoxymagnesium (bis(2,6-di-tert-butyl-4-methyl- phenoxy)magnesium, Mg(OBT) 2 ) derivatives used as additives, on the structure and reactivity of polystyryllithium (PSLi) species in hydrocarbons was studied. The impact of these compounds on the thermal stability of active species and on the reactivity in the styrene anionic polymerization at high temperature was investigated and was compared with that of n,s-dibutylmagnesium (n,s-Bu 2 Mg). Kinetic measurements were carried out in cyclohexane at 100 °C and the thermal stability of polystyryl end-groups was studied at 150 °C in decahydronaphthalene. The presence of BuMgOBT or Mg(OBT) 2 significantly increases the thermal stability of active species compared to dialkylmagnesium or alkylalkoxymagnesium derivatives. Unlike n,s-Bu 2 Mg, BuMgOBT and Mg(OBT) 2 do not contribute to the formation of new PS chains in addition to those produced by PSLi seeds.