Kinetics of the anionic polymerization of methyl methacrylate in 1,2‐dimethoxyethane

Abstract

Earlier kinetic investigations on the anionic polymerization of methyl methacrylate (MMA) in tetrahydrofuran (THF) showed that under appropriate conditions the reaction can be regarded to proceed in an ideal manner1-4). The Arrhenius plots of the rate constants for the propagation reaction of ion pairs with both Na+ and Cs+ as counterions exhibit straight lines which can be regarded to be identical within the limits of experimental error; thus no evidence for the existence of more than one kind of ion pair is given4). The kinetically undifferentiated behaviour of the two counterions, which is in strong contrast to their behaviour in the polymerization of styrene5x6), was explained assuming the propagating species to be contact ion pairs intramolecularly "solvated" by the penultimate or antepenultimate ester group of its own polymer chain (A, B). A B M+:Na* or Cs' Solvation complex B facilitates chain termination occurring at higher temperatures which partly seems to be due to a reaction of the carbanion with the antepenultimate ester group, resulting in a cyclic 8-ketoester end group2v3).A solvent with a higher solvating power, such as 1,2-dimethoxyethane (DME), should result in a lower stability of the intramolecular complex. With sodium as the counterion part of the active centres were expected to exist in the form of externally a) Present address: Lehrstuhl fur Makromolekulare Chemie, Universitat Bayreuth, D-8580 Bayreuth.

Specific Salt Effect of Lithium Perchlorate in Living Anionic Polymerization of Methyl Methacrylate and tert-Butyl Acrylate

“…It is also known that solvent polarity largely affects the reactivity and identity of the propagating species. 39 It was shown that increasing the solvent polarity causes a decrease in isotacticity and a narrowing of molecular weight distribution of PMMA. 40 The polymerization of MMA in toluene/THF (9/1 v/v) mixed solvent was carried out in both the presence and absence of LiClO 4 using DPHLi as an initiator at different temperatures.…”

The effect of TMEDA on the kinetics of the anionic polymerization of methyl methacrylate in tetrahydrofuran using lithium as counterion

“…Thus, many attempts have been made to affect the aggregation equilibria in the polymerization of MMA by using chelating solvents and ligands. Kinetic studies of the polymerization of MMA in the chelating solvent 1,2-dimethoxyethane (DME) of Müller et al [1,[16][17][18] resulted in higher propagation rate constants for Na + and Cs + but lower ones with Li + as counterion. The increase in rate for the larger counterions may be explained by deaggregation of dimers or by an increase of the interionic distance in the ion pairs leading to higher reactivity.…”

Quantum-Chemical (Density Functional Theory) Study of Lithium 2-Methoxyethoxide, Methyl α-Lithioisobutyrate, and Their Mixed Aggregates as Models of the Active Center in the Anionic Polymerization of Methacrylates

“…It is, thus, important to decrease the aggregation or at least to suppress the formation of higher aggregated ester enolates which are of extremely low reactivity. For this aim, polar solvents, especially THF or 1,2-dimethoxyethane, and larger counterions have been used, resulting in a controlled polymerization. , In some more recent approaches, various ligands have been introduced as additives. σ-Ligands, i.e., electron donors, specifically solvate the Li atoms of the ester enolate individual molecules or aggregates, thus preventing their further aggregation.…”