Reactivity control in anionic polymerization of ethylenic and heterocyclic monomers through formation of 'ate' complexes
Résumé
The reactivity and selectivity of active species are the key parameters in the design of living/controlled polymerizations. We have shown that alkyl metal derivatives, such as dialkylmagnesium or trialkylaluminum derivatives, when used as additives to conventional anionic polymerization systems, are very effective mediators for the polymerization control of both ethylenic and heterocyclic monomers. When added to alkali metal alkyl initiators, typically alkyl lithium, for styrene and dienes anionic polymerization they strongly retard the reactivity of the polystyryl and polybutadienyl. propagating species and allow control of the polymerization of styrene under very unusual conditions (bulk, very high temperatures). On the contrary, when used in combination with quite similar alkali-metal-based initiators in the anionic polymerization of ethylene oxide or propylene oxide, these additives drastically enhance the reactivity and the selectivity of the involved propagating species, thus allowing a fast 'living-like' polymerization to proceed at low temperatures in hydrocarbon media.