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

Abstract

Living anionic polymerization of methyl methacrylate can be achieved at −40 °C in tetrahydrofuran (THF) and at −78 °C in toluene/THF (9/1 v/v) using (1,1-diphenylhexyl)lithium as the initiator in the presence of lithium perchlorate (LiClO4) as the additive. Polymerization of tert-butyl acrylate also proceeds in a living manner at −78 oC in THF. Polymers with narrow molecular weight distributions and high initiator efficiencies can be obtained. The use of lithium perchlorate retards the rate of polymerization. The ratio of LiClO4 to initiator has a greater influence in determining the control of polymerization. The beneficial effect of lithium perchlorate is attributed to its efficient interaction with growing ester−enolate ion pairs.

Recent developments in anionic polymerization

“…stability and reactivity); and most importantly thirdly, protection of the ionpair by an extended steric barrier, so that back-biting of the growing anion onto the antepenultimate chain unit is minimized [20]. Two groups of efficient ligated systems have been studied quite recently: firstly, μ-type ligands such as aluminum alkyls [21,22] and some inorganic lithium salts [23]; and secondly, μ/σ-type dual ligands, such as lithium 2-methoxyethoxide (LiOEM) [24*], lithium 2-(2-methoxy)ethoxy ethoxide (LiOEEM) [25,26], and lithium aminoalkoxide [27]. When the anionic species (Li counterion) responsible for the polymerization of methylmethacrylate (MMA) in toluene are ligated by alkylaluminum compounds, living characteristics are observed, and predominantly polymethylmethacrylate) (PMMA) is formed with, however, a fairly broad MWD.…”

“…Well-defined poly-(meth)acrylates have been accordingly synthesized in a toluene/THF (9/1, v/v) mixture at -40°C [23]. Compared to μ-type ligands, μ/σ-type ligands are much more efficient, particularly for the successful block polymerization of MMA and primary acry-lates [24*,26].…”

Surface-Initiated Anionic Polymerization from Nanomaterials

“…However, the double bond of the DPE can be easily reacted by n-or sec-butyllithium (BuLi) to form an adduct with a resonance-stabilized carbanion. The resulting diphenylalkyl anion with lithium as counter cation is reactive for initiation of styrene, diene, and methacrylates [22][23][24]. Therefore, many of the approaches in the surface-initiated anionic polymerization involve the usage of DPE as a precursor co-initiator as shown in Scheme 3.…”

Poly(methyl methacrylate) (PMMA)

“…These initiator systems effectively induce the living anionic polymerization of MMA to give the PMMA predicted molecular weight and narrow molecular weight distributions (M w /M n < 1.1). The systems include the bulky and p-conjugated carbanions in the presence of common salts or Lewis acidic additives [9][10][11], lithium enolate [12], silyl ketene acetal in conjunction with nucleophilic activator [13], and metal-free anion [14].…”