Methyl methacrylate methoxide anion polymerization

Some abnormalities were reported in the initiations of methyl methacrylate polymerizations in toluene by butyllithium. Their nature is such that they suggest the possibility of more than one reaction taking place simultaneously. One, which must be the major one, is that of the oiganomet-allic compound reacting with the carbon-to-carbon double bond as shown above. The other, minor one, may be with the carbon-to-oxygen double bond. The major reaction produces methyl methacrylate anions. The minor reaction, however, yields butyl isopropenyl ketone with an accompanying formation of lithium methoxide ... 

Lithium methoxide does not initiate polymerizations of methyl methacrylate. The ketone molecules, however, react with carbanions on the growing chain. The resultant anions are less reactive than methyl methacrylate anions and can only add new methyl methacrylate monomers slowly. Once added, however, the reaction proceeds at a normal rate. Polymerizations of methyl methacrylate in polar solvents, on the other hand, proceed in what might be described as an ideal manner with formations of only one kind of ion pair. ... 

Lithium methoxide does not initiate polymerizations of methyl methacrylate. The methoxide molecules, however, react with carbanions on the growing chain. The resultant anions are less reactive than methyl methacrylate anions and can only add new methyl methacrylate monomers slowly. 

Polar Vinyl Monomers. The anionic polymerization of polar vinyl monomers is often complicated by side reactions of the monomer with both anionic initiators and growing carbanionic chain ends, as well as chain-termination and chain-transfer reactions. However, s5mthesis of polymers with well-defined structures can be effected under carefully controlled conditions. The anionic polymerizations of alkyl methacrylates and 2-vinylpyridine exhibit the characteristics of living polymerizations under carefully controlled reaction conditions and low polymerization temperatures to minimize or eliminate chain-termination and chain-transfer reactions. The proper choice of initiator for anionic polymerization of polar vinyl monomers is of critical importance to obtain polymers with predictable, well-defined structures. As an example of an initiator that is too reactive, the reaction of methyl methacrylate (MMA) with w-butyllithium in toluene at -78°C produces approximately 51% of lithium methoxide by attack at the carbonyl carbon (85). 

It has been suggested that the broad molecular weight distribution of poly(methyl methacrylate) prepared in toluene with anionic initiator could be explained in terms of a combination of two narrower distributions produced simultaneously occurring mechanisms(1). Cottam et al.(2) suggested the existence of two active species uncomplexed and complexed with lithium methoxide, respectively, in the polymerization of MMA with BuLi. Recently it was reported that in the polymerization of MMA in a mixture of toluene and THF with Grignard reagent the polymers obtained consist of two components, methanol-soluble and methanol-insoluble polymers, which are considered to form at two distinct and independent active centers(3). In the polymerization of methyl a-ethylacrylate by BuLi in toluene there exist two types of active species which produce isotactic and syndictactic polymers, respectively(4). 

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