Macromol. zyxwvutsr Rapid Commun. zyxwvu 15,517-525 (1994) zyxwv 517 zy Mechanism of anionic polymerization of (meth)acrylates in the presence of aluminium alkyls, 1 13C NMR studies of model compounds in toluene Helmut Schlaad, Axel H. E. Miiller* Institut fur Physikalische Chemie, Universitat Mainz, Welder-Weg 15, D-55099 Mainz, Germany Heinz Kolshorn Institut fur Organische Chemie, Universitat Mainz, Becher-Weg 18, D-55099 Mainz, Germany (Received: January 25, 1994; revised manuscript of February 17, 1994) Introduction During the last five years several pieces of work have been published describing the ‘living’ polymerization of methacrylates in the presence of aluminium alkyls zy -4). The polymerizations can be carried out even at ambient temperature in non-polar solvents like toluene without losing their ‘living’ character. At low temperatures highly syndio- tactic polymers are found, in strong contrast to aluminium-free polymerization. However, very little is known about the effect of aluminium alkyls on the mechanism of polymerization. Based on NMR investigations of the initiating system tert-butyllithium/aluminium alkyl, Hatada et al. 5, suggested that the dimeric aluminium alkyl is coordinated to both the metalated enolate structure of the living chain end and to the penultimate ester group of the polymer. This structure is proposed in order to explain the syndiotactic propagation. On the contrary, Ballard et al. 2, and Haddleton et al. 3, formulate the propagating species to be an enolate bound to a mixed aluminium/lithium alkyl gegenion which is supposed to sterically hinder termination reactions (“screened anionic polymerization”). Inoue et al. 4, use aluminium porphyrin initiators. In that case the aluminium alkyl was shown to have no effect on the structure of the living chain end. An activation of the monomer by the aluminium alkyl is supposed to be responsible for the dramatic acceleration of the polymerization (“high-speed living polymerization”) zyxwvut ‘I. This effect of Lewis acids has been long known for free-radical polymerization of vinyl monomers ’). Similarly, syndiotactic poly(2-vinylpyridine) is obtained with a tert-butyllithium/ aluminium alkyl initiator *I. Due to this correspondence and the isoelectronic struc- ture of the monomers, similar mechanisms of polymerization were assumed9). In this series of papers we wish to present NMR and kinetic studies of the polymeri- zation of methyl methacrylate (MMA) and butyl acrylate in toluene in the presence of aluminium alkyls. Here, we report a I3C NMR study of the structures of complexes of aluminium alkyls with models of the chain end of living PMMA and the in-chain ester z 0 1994, Huthig & Wepf Verlag, Basel CCC 1022-1 336/94/$02.00