The system AlR 3-2,2′-dipyridyl as a stimulator of anionic polymerization

Abstract

It has been established that the system AlR 3-2,2′-dipyridyl is an active initiator for the low temperature anionic polymerization of monomers of methacrylic and acrylic series. With PMMA as an example, it has been shown that the polymers formed are syndiotactic and the temperature for the start of their thermal decomposition is rather higher than that for polymers obtained by the use of the customary anionic stimulators. The process belongs to the anionic-coordination type: complex-formation between the monomer and the active site in the stages of initiation and chain propagation is a necessary condition for the development of polymerization. In order to create the catalytic activity, the components of the initiator must be held beforehand in the absence of the monomer, during which the aluminium alkylamides that are active in polymerization are formed. The rate of the process is determined not only by the concentration of the components of the initiator but also by the stoichiometric ratio [AlR 3] : [2,2′-dipyridyl]. The latter fact causes the rate of formation of the aluminium alkylamides to depend on the ratio between the components of the initiator. It has been shown that, at the same time as the formation of the catalytically active compounds, an “ageing” process occurs in the catalyst, which is reversible in character.