Poly(methyl methacrylate)-6-poly(i eri-butyl acrylate) (PMMA-6-PtBA) copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and tertbutyl acrylate (tBA) in THF at -78 °C. Although the order of monomer addition makes a difference on the initiation efficiency, it has no significant effect on the final achievement. Monoand bifunctional initiators based on alkali metals can be used. When the initiators are modified by LiCl as a ligand, the polymerization of each block appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution is narrow. Size exclusion chromatography supports the absence of homo-PtBA in the PtBA-6-PMMA samples. The PtBA blocks can be quantitatively hydrolyzed into polyacid ones as supported by titration and NMR analysis.

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It has been previously shown that µ-coordinating inorganic salts, such as LiCl, were effective in preventing the anionic polymerization of methacrylic esters and hindered alkyl acrylates from being disturbed by secondary transfer and termination reactions. That strategy has opened the way to the "living" polymerization of these monomers and their controlled sequential polymerization with monomers lacking a carbonylconjugated group. That control is however limited to THF at low temperatures for methyl methacrylate and tert-butyl acrylate. It is reported now that the polymerization mechanism remains strictly controlled in apolar solvents, such as toluene, and at temperatures as high as 0 °C, when crown ethers are used in relation to their capability of chelating the alkali-metal counterion and surrounding it with a steric barrier blocking a large enough space area around the metal-containing ion pair.

A mixed complex of a polydentate lithium alkoxide, i.e., lithium 2-(2-methoxyethoxy) ethoxide (LiOEEM), and of a mono-or bisfunctional organolithium initiator, i.e., (diphenylmethy1)lithium (DPMLi) or lithium naphthalene/diphenylethylene, has been used to synthesize well-controlled AB (BA), ABA, and BAB block copolymers of methyl methacrylate (MMA) (A) and 2-ethylhexyl acrylate (2EtHA) (B), irrespective of the monomer addition order. Although the 2EtHA block copolymerization initiated with monofunctional living PMMA macroanions at -78 "C in a 75/25 toluene/THF mixture gives rise to a precisely-tailored PMMA-b-P2EtHA diblock polymer, the reverse sequence, i.e., from P2EtHA anions to the MMA type monomer, always results in contamination by homo-P2EtHA. This has been interpreted in terms of the short shelf lifetime of P2EtHA anions present. Nevertheless, a pure P2EtHA-b-PMMA type diblock copolymer can be produced at -100 "C, while keeping other conditions unchanged. More importantly, a well-controlled PMMAb-P2EtHA-b-PMMA triblock copolymer has been prepared through a three-stage process with a monofunctional initiator, acutally providing a potential pathway toward the direct synthesis of a novel type of fully acrylic thermoplastic elastomer, instead of the more complicated hydrolysis/transalcoholysis process previously demonstrated by us. IntroductionIt has been recently demonstrated by us that d o dual polydentate lithium alkoxides, such as 242-methoxyethoxy) ethoxide (LiOEEM), can efficiently form a stable and bulky p l a complex with lithium ester enolates in solution' and should consequently be very effective in

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