Influence of monomer concentration on the structure of poly(methyl methacrylate) polymerized by butyllithium

Abstract

The polymerization of methyl methacrylate has been studied in toluene and tetrahydrofuran solution at −78°C using butyllithium as catalyst. The structure of the polymer produced was determined by analysis of the α‐methyl groups using 100 MHz NMR. It is shown that in a noncomplexing solvent such as toluene, the number of isotactic triads increases from 70% to 93% as the monomer concentration during polymerization is reduced from 5 mole/l. to approximately zero. The value of Pss/Pis depends strongly on monomer concentration, and hence any calculations regarding penultimate effects in such systems should be made at close to zero monomer concentration. In the THF solution the penultimate effect is nearly independent of monomer concentration, and both Pii/Psi and Pss/Pis are close to unity. The results may be explained in terms of a mechanism of the polymerization process in which toluene does not complex with the active site, while monomer and THF are weak and strong complexing agents, respectively.

Evaluation of a Gas Chromatographic Method for the Determination of Glass Transitions in Polymers

“…The PMMA samples are labeled according to tacticity of the predominant triad; heterotactic PMMA was purchased from Fisher Scientific Co.; syndiotactic and isotactic PMMA were polymerized with butyllithium catalyst at -78°in THF and toluene, respectively, as described elsewhere. 5 The resultant tacticity was determined by nmr at 100 MHz for the syndiotactic (A) and isotactic (B) samples0 (Chart I). Narrow MWD anionic polystyrenes were obtained from Pressure Chemical Co. Styrene-butadiene polymers were obtained from Cellomer Associates, Inc. Plasticizer was Eastman Kodak di-n-octyl o-phthalate.…”

Rate Constants of the Tactic Monomer Addition in the Anionic Polymerization of Methyl Methacrylate in THF with Cesium as Counterion

“…These requiriments are not matched by our results (cf. Table I) as well as by the results of Amerik et al 4 using Li+ as counterion.…”

Stereochemistry of Acrylate Polymerization in Toluene Using n-BuLi

“…31, No. 5,1999 Concerning the anionic polymerization of MA and tBA, the effects observed in this work have not been reported although there have been studies 17 · 18 on the reaction stereochemistry.…”