| The use of 2-methyleneallyl dipotassium and some of its derivatives as anionic initiators for the preparation of polymers possessing controlled molecular architecture via anionic addition polymerization of styrenic and acrylic monomers was investigated.; A convenient synthesis of 2-methyleneallyl dipotassium, based upon the dehydrohalogenation-metalation of tert-butyl chloride by Lochmann's/Schlosser's heterogeneous complexed base, was developed. This synthesis yielded 2-methyleneallyl dipotassium in {dollar}sim{dollar}85% yield, based on tert-butyl chloride.; Several methods for generating soluble initiating species from 2-methyleneallyl dipotassium were explored. Seeding of 2-methyleneallyl dilithium with {dollar}alpha{dollar}-methylstyrene in THF at 0{dollar}spcirc{dollar}C, and preparation of 1,1-di(3,3-diphenyl,3-lithiopropyl)ethene in 95/5 benzene/THF solution for styrene polymerization were both found to yield soluble initiating species, thus improving control of polymer molecular weight versus previous methods. However, due to THF cleavage in the case of the former method, and a large number of steps in the case of the latter method, neither method provided precise control of polymer molecular weight.; {dollar}sp1{dollar}H NMR analysis revealed that polystyrenes initiated with olefinic dianions were devoid of olefin functionality, while poly(methyl-methacrylate) initiated with an olefinic dianion showed the expected amount of olefin functionality. It was postulated that, in the case of styrene polymerization, an intramolecular cyclization takes place between the olefinic moiety of the initiator fragment and one of the propagating chain ends. This determination was supported by {dollar}sp2{dollar}H NMR analysis of a poly({dollar}alpha{dollar}-methylstyrene) oligomer prepared using perdeuterated 2-methyleneallyl dipotassium as the initiator. |
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