Chemoselective Polymerization of Polar Divinyl Monomers with Rare-Earth/Phosphine Lewis Pairs

Abstract

This work reports the chemoselective polymerization of polar divinyl monomers, including allyl methacrylate (AMA), vinyl methacrylate (VMA), and 4-vinylbenzyl methacrylate (VBMA), by using simple Lewis pairs comprised of homoleptic rare-earth (RE) aryloxide complexes RE(OAr)3 (RE = Sc (1), Y (2), Sm (3), La (4), Ar = 2,6-tBu2C6H3) and phosphines PR3 (R = Ph, Cy, Et, Me). Catalytic activities of polymerizations relied heavily upon the cooperation of Lewis acid and Lewis base components. The produced polymers were soluble in common organic solvents and often had a narrow molecular weight distribution. A highly syndiotactic poly(allyl methacrylate) (PAMA) with rr ~88% could be obtained by the scandium complex 1/PEt3 pair at −30 °C. In the case of poly(4-vinylbenzyl methacrylate) (PVBMA), it could be post-functionalized with PhCH2SH. Mechanistic study, including the isolation of the zwitterionic active species and the end-group analysis, revealed that the frustrated Lewis pair (FLP)-type addition was the initiating step in the polymerization.

Lewis pairs polymerization of polar vinyl monomers

“…Mechanistic investigations revealed that the LPP was initiated by the ninemembered addition intermediate resulting from the intramolecular 1,4-addition of rare-earth metal complexes to the monomer. Later in 2018, they reported the polymerization of conjugated polar alkenes, such as MMA, t BuMA, DMAA, and FMA as well as divinyl monomers AMA, VMA, and VBMA, by LPs consisting of homoleptic rare-earth aryloxides (Ln = Sc, Y, Sm, and La) as the LA and phosphines or NHCs as the LBs [73,74]. Among the investigated monomers, polymerization of MMA was relatively controlled over the M n and MWD in spite of low I*.…”

Solventless Synthesis and Patterning of UV‐Responsive Poly(allyl methacrylate) Film

“…[10,[14][15][16][17][18][19] So far, to retain the allyl group of AMA for further reactions, harsh conditions such as low temperature and/ or additional additives are usually required during polymerization. [7,11,20] Vapor deposition offers a more advantageous approach in synthesizing crosslinked films than traditional liquidbased methods, since polymerization and crosslinking take place during film formation as opposed to liquid-based film fabrication. Vapor-based approaches could also compensate for the shortcomings caused by the use of organic solvents, such as insoluble reactants, residual contaminants from solvent, and damage to substrates.…”

“…However, radical polymerization of AMA under normal conditions may lead to crosslinking or cyclization of the side chain, depleting allyl groups at an early stage of polymerization (Figure c) . So far, to retain the allyl group of AMA for further reactions, harsh conditions such as low temperature and/or additional additives are usually required during polymerization …”

“…[5,[7][8][9] Allyl methacrylate (AMA) is one of the most widely studied ADMs containing two different CC bonds, the relatively reactive vinyl group and the less reactive allyl group. [10,11] The films with further functionalization opportunity and extend the choice of patterning substrates to solvent-sensitive materials and non-planar surfaces. [21,26]…”

Lewis Pair Polymerization for New Reactivity and Structure in Polymer Synthesis

“…Firstly, the studies on the controlled or chemoselective addition polymerizations of conjugated polar alkene monomers represent four articles in this Special Issue [ 5 , 6 , 7 , 8 ]. Specifically, the controlled and efficient polymerizations of polar monomers such as methyl methacrylate (MMA), n -butyl methacrylate ( n BMA), and γ -methyl- α -methylene- γ -butyrolactone ( γ MMBL) catalyzed by the sterically hindered aryloxide-substituted alkylaluminum/ N -heterocyclic carbene (NHC) Lewis acid/base catalyst system were reported by Hong and co-workers [ 5 ].…”