Studies on the Mechanism of Polymerization of Ethyl Methacrylate with BuLi in Toluene Using Perdeuterated Monomer and Multiplicity of Active Species

Abstract

ABSTRACT:Perdeuterated ethyl methacrylate was polymerized with BuLi in toluene at -78°C. The resulting product consisted of syndiotactic and isotactic polymers and oligomers, indicating the existence of multiple active species. The structure of each component was confirmed by 1 H NMR spectroscopy. Most of the oligomers had butyl isopropenyl ketone units at the chain ends. The isotactic polymer contained one ketone unit near the beginning of the chain, while the syndiotactic polymer had about two ketone units located near the beginning and interior sequence of the chain. The mechanism of polymerization is discussed in detail, and also the structures of active species are proposed from the standpoint of the association oflithium alkoxide formed in the system, that is, the syndiotactic active species are associated with the alkoxide while the isotactic species are not.KEY In the anionic polymerizations of some a-substituted acrylates with butyllithium (BuLi), it was confirmed that isotactic and syndiotactic polymers are formed independently in the same reaction system. 1 -3 This suggests the existence of multiple active species in the polymerization. The polymerization of ethyl methacrylate (EMA) with BuLi in toluene gives methanol-soluble and -insoluble fractions.3 The methanol-insoluble fraction was found to consist syndiotactic polymer, and the methanolsoluble fraction to contain the isotactic polymer and the oligomer. These two fractions are easily separated by pouring the polymerization mixture into methanol. No syndiotactic polymer was obtained when the polymerization temperature was above -20°C or 1,1-diphenylhexyllithium was used as an initiator instead of BuLi. These results were explained in terms of the multiplicity of active species.3 However, the difference in structure other than tacticity among the syndiotactic and isotactic polymers and oligomers was not clear.Recently we have developed a new method for studying the polymerization reaction, in which the perdeuterated monomer is polymerized with an undeuterated initiator and the product is analyzed by 1 H NMR spectroscopy. 4 -8 The study on the anionic polymerization of methyl methacrylate (MMA) with BuLi in toluene 4 and in tetrahydrofuran (THF) 5 by the perdeuterated monomer technique revealed that butyl isopropenyl ketone, formed through the attack of BuLi on the carbonyl double bond of MMA, was incorporated into the polymer and oligomer chains. The manner of incorporation of the ketone unit in the syndiotactic polymer formed in THF differed from the case of the isotactic polymer formed in toluene. These findings lead us to investigate the structural differences in the isotactic and syndiotactic polymers of EMA formed in toluene by the perdeuterated monomer method.In this study, perdeuterated EMA was synthesized and polymerized with BuLi in toluene at 971

Highly Isotactic and Living Polymerization of Ethyl Methacrylate with t-C4H9MgBr in Toluene and the Preparation of Block and Random Copolymers with High Stereoregularity

“…22, No. 5,1990 copolymerization. Thus the living character of both higher and lower molecular weight poly(EMA) propagating species at -60°C is indicated.…”

“…3,4 Stereoregularity in the anionic polymerization of methacrylates usually depends on the structure of the ester groups. For example, in the polymerization of ethyl methacrylate (EMA) with n-C4H9Li in toluene at -78°C, there are at least two types of active species which give isotactic and syndiotactic-rich polymers, 5 while the polymerization of MMA under the same conditions gives isotactic-rich polymer only.…”

Syntheses and applications of graft copolymers from poly(1,1-diphenylethylene-co-divinylbenzene)s

“…Carbonyl attack by the initiator occurs more largely in the polymerization with n-C4H9Li of MMA than in that of t-BuMA (Hatada et al, 1979(Hatada et al, ,1982. Cross-linking by the association of the PMMA branches, like stereocomplex formation, could be another possible explanation.…”

Studies on the Polymerization of Methyl Methacrylate with Butylmagnesium Chloride by the Aid of Totally Deuterated Monomer—Structures of Polymerization Products and Fate of Initiator

“…27 In the polymerization of ethyl methacrylate by butyllithium in toluene, the multiplicity of active species is caused by the formation of lithium ethoxide in the initiation process, and the propagating species coordinated with the ethoxide forms a syndiotactic polymer while the species free from the alkoxide forms an isotactic one. 17 In the polymerization by C 4 H 9 MgCl, CH 3 0MgCl should be formed through the carbonyl addition of the initiator to MMA (11) and the intramolecular cyclization (6). The presence of CH 3 0MgC1 may be one of the factors causing the coexistence of isotactic-ftavoring and syndiotactic-favoring propagating species.…”