Polymerization of Methyl Methacrylate Initiated by a Divalent Samarium Phenoxide Complex with an Alkyl Aluminium Compound

Abstract

A divalent samarium complex that bears two bulky phenoxide ligands promotes the living polymerization of methyl methacrylate in the absence of cocatalyst. The initiation involves a tail‐to‐tail coupling reaction of the samarium‐enolate radical followed by a one‐electron reduction of the monomer with the divalent samarium initiator. The polymerization takes place stereospecifically and the samarium initiator affords highly syndiotactic poly(methyl methacrylate). The stereoregularity of the polymer is variable with the ratio of the samarium initiator to aluminium compound (2,6‐di‐tert‐butyl‐4‐methylphenoxy)2AlMe. The polymer obtained when the [Al]/[Sm] ratio is 4.0 has a unique tacticity, [mm]/[mr]/[rr] = 42:11:47, and the polymer has a melting point at 161 °C, which suggests the formation of a stereocomplex between syndiotactic and isotactic poly(methyl methacrylate).

Rare Earth Metal-Mediated Precision Polymerization of Vinylphosphonates and Conjugated Nitrogen-Containing Vinyl Monomers

“…The mechanism was identified by 13 C-labeled initiators and methyl end groups in the final PMMA polymer, respectively . Group 4 complexes require a cocatalyst for activation, and therefore, the corresponding counterions can affect the stereoregularity or polymerization activity. , The mechanism of group 4 GTP is either mono- or bimetallic. ,− …”

“…161 Group 4 complexes require a cocatalyst for activation, and therefore, the corresponding counterions can affect the stereoregularity or polymerization activity. 102,163 The mechanism of group 4 GTP is either mono-or bimetallic. 102,164−166 In most cases, trivalent rare earth (RE) metal complexes are used for the polymerization of MMA and other (meth)acrylates, as they are highly active, they initiate via nucleophilic transfer, and the oxidation state Ln 3+ leads to stable compounds.…”

Synthesis of highly syndiotactic polymers by discrete catalysts or initiators

“…A divalent non-metallocene samarium complex supported by the bulky phenoxy ligand, (BHT) 2 Sm(THF) 3 (38), promotes living polymerization of MMA in toluene at À78 C, producing st-PMMA (M n ¼ 43 KDa, PDI ¼ 1.08, rr ¼ 90%) with good activity (TOF ¼ 200 h À1 ). 119 The effect on the polymerization by adding an increasing amount of MeAl(BHT) 2 was performed; increasing the [Al]/[Sm] ratio from 0 to 5 led to a decrease in rr from 90 to 20%, accompanied by an increase in mm from 1 to 68%, and a nearly constant mr. Group IV chiral metallocenes, especially in their cationic forms, have achieved phenomenal levels of success performing as homogeneous, single-site, stereospecific catalysts for polymerization of nonpolar a-olefins to stereoregular polymers with tailored stereomicrostructures. 120 Such successes have allowed for the establishment of a strong correlation between the symmetry of such chiral metallocenium catalysts and the stereomicrostructure of the resulting polymers.…”

Lanthanide borohydrido complexes for MMA polymerization: syndio‐ vs iso‐ stereocontrol

“…A good stereocontrol could be obtained at 0 °C, by adding an aluminum phenoxide (run 3), known as an activator for MMA polymerisation. 22,35 This additive has a drastic effect in the absence of alkyl co-catalyst, allowing the formation of highly syndiotactic PMMA (run 1). With BuLi as an alkylating agent, activity is also noticeably increased in the presence of the aluminium additive (95 % in 3 h for run 3; to be compared to 92 % in 23 h for run 4), whereas the tacticity is unchanged.…”