Crystalline acrylic polymers. II. Mechanism studies

Abstract

The polymerization of methyl methacrylate and isopropyl acrylate in toluene with phenyl‐H3‐magnesium bromide has been studied at 0 and −70°C., respectively. Comparison of number‐average molecular weights calculated from measurement of radioactivity and from measurements of appropriate colligative properties has shown that there is one and only one phenyl group per chain. Thus, initiation in this system is by 1,4‐addition of the organomagnesium compound to the monomer. Methyl methacrylate, isopropyl acrylate, ethyl acrylate, and methyl acrylate were polymerized in toluene with phenylmagnesium bromide as the initiator. Isolation and identification of all the products have shown that, in addition to polymer, there are formed small amounts of two ketones and a hydrocarbon. Data are presented indicating that the principal mode of termination is via an intramolecular cyclization to give chains having a β‐ketoester group on the end (arising from intramolecular reaction). A rationale for the stereospecificity, the termination reaction, and the large ratios of weight‐average to number‐average molecular weight in these polymerizations is proposed.

The Organometallic Polymerization of (Meth)acrylates: An Overview

“…In contrast, chain transfer is facile for acrylates due to the presence of an acidic proton at the carbonyl a-position (10,13,(33)(34)(35)(36). Again, only bulky monomers such as isopropyl and f-butyl acrylate (*BuA), may be polymerized anionically to high conversion with even moderate degrees of control.…”

“…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.…”

“…Side reactions involving nucleophilic attack at the ester group render anionic (meth)acrylate polymerization nonliving under typical conditions (11)(12)(13)(14)(15). 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).…”

Anionic block copolymerization of methyl methacrylate in the presence of alkali and alkali–earth metal salts

“…',, It is well known indeed that this polymerization is complicated by side and termination reactions due to the possible attack of carbonyl groups by the carbanions and also by internal cyclizations in apolar solvents?. 4 Therefore, in contrast to the situation with styrene and dienes, the anionic polymerization of MMA proceeds predictably only with careful selection of solvent, temperature, and initiator. Moreover, block copolymers of hydrocarbons (e.g., styrene) and MMA can only be prepared by first forming the nonpolar segment and utilizing the resulting polymeric anion to initiate the polymerization of the methacrylic monomer.…”

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

“…Goode and his coworkers 10 studied the initiation and termination processes in the polymerization of MMA by tritium-labeled phenylmagnesium bromide through a detailed analysis of the low molecular weight products of polymerization. Yasuda and his coworkers 11 investigated the elementary steps of the polymerization reaction by butylmagnesium bromide.…”