Anionic Polymerization of Methyl Methacrylate as Promoted by a N-Butyl Lithium-Pyridazine-Polyether Alkoxide Based Complex Initiator System

摘要

Polymerization of methyl methacrylate was conducted using a n-butyl lithium/pyridazine system as initiator in tetrahydrofuran (THF) and toluene.Special attention was focused on using some lithium polyether alkoxides as polymerization is promoted at ambient temperatures.The positive effects of these mu/sigma-type ligands such as lithium 2-(2-methoxyethoxy)ethoxide and lithium 2-(methoxy)ethoxide on controlling the living character,molecular weight,stereoregularity and yield of the produced polymers were all demonstrated.It was found that initiator/lithium-2-(methoxy)ethoxide in a 1/10 ratio gives the most controlled polymerization.All products were then characterized by size exclusion chromatography (SEC),proton nuclear magnetic resonance (~1H NMR) and differential scanning calorimeter (DSC).The molecular weight distributions obtained were as narrow as 1.28 and the glass transition temperatures were comparable with that of a syndiotactic PMMA and approximately 100% conversions achieved.Moreover,the effect of the polarity of the solvents on the association equilibrium has been discussed.It was found that the molecular weight of the produced polymethylmethacrylate could be better controlled in THF than in toluene.