Reactions of models of the growth center during anionic polymerization of methacrylate esters

Abstract

Reactions of α‐lithioisobutyric acid esters were studied as models of partial reaction taking place during anionic polymerization of methacrylate esters. The rates of selfcondensation reactions and condensations with nonmetalated esters were determined for these models. In both cases ketoesters were the final products. Besides esters of α,α,α′‐trimethylglutaric acid expected according to Michael's reaction scheme the addition of methacrylate esters to α‐lithio esters also yielded oligomeric compounds due to repeated addition of methacrylate esters. The α‐lithio oligomers of methacrylate esters underwent cyclization condensation which gave rise to esters of substituted cyclohexanonedicarboxylic acids. The alkali metal alkoxides slowed down all the condensation reactions of α‐lithio esters investigated here. Such effect of alkoxides also appeared in the cyclization condensation of compounds formed by repeated addition of methacrylate esters, because in the presence of alkoxides the reaction mixture contained a higher amount of higher molecular weight compounds than in a system without alkoxide. The effect of alkoxides observed here is in accordance with the view that the cyclization condensation is one of the termination reactions of the anionic polymerization of methacrylate esters.

The in situ formation of a new initiator system for the syndiotactic anionic polymerization of methyl methacrylate in toluene at 0°C

“…This dependence of F can be accounted for as follows. According to Lochmann et al [7] esters of α-lithioisobutyric acid have a limited stability in hydrocarbons and they react by self-condensation (i.e. 2LiMe 2 CCOOEt→LiMe 2 CCOCMe 2 COOEt+LiOEt) and by condensation with the parent non-metalated ester (i.e.…”

“…It is well known that α-lithio esters are very effective initiators for the polymerization of (meth)acrylates [5][6][7]. These compounds have as yet been prepared in the pure state, mostly by metalation of esters using substituted metal amides in aliphatic or aromatic hydrocarbon solvent even at room temperature [8][9].…”

“…However, this procedure involves the separate synthesis of both the polydentate lithium alkoxide and DPHLi, the use of the latter being economically prohibitive. The purpose of this communication is to report on the discovery of a new concept which allows an efficient 'in situ' one-pot synthesis of ligand and initiator adduct, a possible answer to that economical problem.It is well known that α-lithio esters are very effective initiators for the polymerization of (meth)acrylates [5][6][7]. These compounds have as yet been prepared in the pure state, mostly by metalation of esters using substituted metal amides in aliphatic or aromatic hydrocarbon solvent even at room temperature [8][9].…”

The Organometallic Polymerization of (Meth)acrylates: An Overview

“…The most common process is intramolecular "backbiting" of the active endgroup to the ante penultimate ester unit of the polymer chain (Equation 1) (13,(16)(17)(18). This produces a nonreactive cyclic ketone endgroup and an alkoxide ion and results in lowered initiator efficiency and inflated molecular weights.…”

“…The use of these conditions in conjunction with bulky, less nucleophilic initiators, such as alkali metal 1,1-diphenylalkanes (40,41) and aromatics (42) and branched Grignard reagents (43), has allowed the preparation of relatively monodisperse PMMA (PDI < 1.20) with good molecular weight control. Alkali metal enolates, which mimic the active endgroup of the polymerization, are especially effective in this regard (18).…”