New Ligands for the Living Isotactic Anionic Polymerization of Methyl Methacrylate in Toluene at 0 °C. 1. Ligation of Butyllithium by Lithium Silanolates

Abstract

sBuLi and tBuLi have been combined with a new family of ligands, i.e. lithium silanolates, and used as initiators for the ligated anionic polymerization (LAP) of methyl methacrylate (MMA) in toluene at 0 °C. Compared to other known µ-ligands, the accordingly formed Bu(Me 2)SiOLi are more efficient stabilizers for the active centers. Under appropriate reaction conditions, a fast polymerization proceeds quantitatively without self-termination at 0 °C and leads to high molecular weight polymer of narrow molecular weight distribution (M h w/M h n < 1.2) and high isotacticity (90% isotactic triads).

Recent developments in anionic polymerization

“…According to a 'process-friendly' method, sec-butyllithium is reacted with hexa(octa)-methyl cyclotri-(tetra)siloxane (D 3 or D 4 ) leading to sec.C 4 H 9 -Si(CH 3 ) 2 OLi, which is the actual ligand for unreacted sec.BuLi and, later on, for the propagating species of the MMA type. Figure 3 illustrates this cascade-type of reaction, which, under optimized experimental conditions (particularly the initial sec.BuLi: D 3 [or D 4 ] molar ratio) leads to a single mixed complex, as confirmed by multinuclear NMR spectroscopy [38]. This active mixed complex promotes the quantitative living polymerization of MMA in toluene within 1 h at 0°C, such that PMMA up to 100,000 g/mol -1 can be synthesized with a narrow MWD (~ 1.1).…”

Anionic polymerization of methyl methacrylate using tetrakis[tris(dimethylamino)phosphoranylidenamino] phosphonium (P5+) as counterion in tetrahydrofuran

“…One possibility is the use of various ligands in conjunction with classical anionic initiators. r-Ligands, such as crown ethers 6) , cryptands 7,8) , tertiary amines 9,10) ; l-ligands, such as alkali alkoxides 11,12) halides 2, 13) , perchlorates 14,15) , aluminum alkyls [16][17][18][19] , and r, l-ligands, such as alkoxyalkoxides [20][21][22][23] , aminoalkoxides 24) , and silanolates [25][26][27] have been used with much success.…”

Synthesis and thermal properties of triblock copolymers of methyl methacrylate using combination of anionic and controlled radical polymerization: Poly(methyl methacrylate) center block bearing different microstructures

“…It is well documented in the literature that polymerization of methyl methacylate (pMMA) macro anions in tetrahydrofuran (THF) at -78 ºC in the presence of -type ligand are "true living" anionic process [22,23]. This approach offers interesting prospects for the macromolecular engineering in designing macromolecules with well-defined molecular architecture.…”