Ultrafast Synthesis of Ultrahigh Molar Mass Polymers by Metal-Catalyzed Living Radical Polymerization of Acrylates, Methacrylates, and Vinyl Chloride Mediated by SET at 25 °C

Abstract

Conventional metal-catalyzed organic radical reactions and living radical polymerizations (LRP) performed in nonpolar solvents, including atom-transfer radical polymerization (ATRP), proceed by an inner-sphere electron-transfer mechanism. One catalytic system frequently used in these polymerizations is based on Cu(I)X species and N-containing ligands. Here, it is reported that polar solvents such as H(2)O, alcohols, dipolar aprotic solvents, ethylene and propylene carbonate, and ionic liquids instantaneously disproportionate Cu(I)X into Cu(0) and Cu(II)X(2) species in the presence of a diversity of N-containing ligands. This disproportionation facilitates an ultrafast LRP in which the free radicals are generated by the nascent and extremely reactive Cu(0) atomic species, while their deactivation is mediated by the nascent Cu(II)X(2) species. Both steps proceed by a low activation energy outer-sphere single-electron-transfer (SET) mechanism. The resulting SET-LRP process is activated by a catalytic amount of the electron-donor Cu(0), Cu(2)Se, Cu(2)Te, Cu(2)S, or Cu(2)O species, not by Cu(I)X. This process provides, at room temperature and below, an ultrafast synthesis of ultrahigh molecular weight polymers from functional monomers containing electron-withdrawing groups such as acrylates, methacrylates, and vinyl chloride, initiated with alkyl halides, sulfonyl halides, and N-halides.

Recent developments in metal-catalyzed living radical polymerization

“…17,61,62 More recently, Percec and co-workers proposed that the Cu(0)-based living radical polymerization proceeds via a single-electron transfer mechanism under certain conditions and that their systems are highly effective for the very fast living radical polymerization of various monomers, leading to well-controlled high-molecular weight polymers with narrow MWDs. [63][64][65][66] In contrast, the Cu(I)-based systems in the presence of reducing agents, such as tin(II) 2-ethylhexanoate, ascorbic acid, Cu(0) and radical initiators, also induced an efficient living radical polymerization, in which the accumulated Cu(II) species changed into the active Cu(I) species via the reduction by these additives. [67][68][69][70] Although the working mechanisms of Cu(0) are still controversial and may depend on the conditions, it is clear that the use of lower oxidation metal species is important for constructing highly catalytic systems.…”

Quartz crystal microbalance study of the kinetics of surface initiated polymerization

“…To simplify, we assumed that the surface confined polymerization was mechanistically the same as the solution polymerization was. Furthermore, we did not consider detailed mechanism of how the metal complex catalyzed this radical polymerization: whether it is ATRP mechanism [60] or SET mechanism [61] . And we only considered radical combination as the source of radical loss.…”

Synthesis of poly(di[methylamine]ethyl methacrylate)‐b‐poly(cyclohexyl methacrylate)‐b‐poly(di[methylamine]ethyl methacrylate) amphiphilic triblock copolymers by ATRP: Condensed‐phase and solution properties

“…[1][2][3][4][5][6][7][8] This polymerisation can be initiated with different alkyl halides, 5,6,[9][10][11][12][13] sulfonyl halides, [14][15][16][17] and N-halides, 18,19 diverse catalyst/ligand systems, [20][21][22][23][24][25][26] and can be carried out in organic and aqueous media [5][6][7][8][9][10][11][12][13][14]27 as well as in carbon dioxide, ionic liquids, or other solvent of low volatility 18,28,29 principally for styrene, meth (acrylate), and acrylonitrile monomers. Its success is due to the effective minimization of termination and chain transfer reactions, which allows developing a great variety of molecular architectures and functionalities with controlled molecular weights and low polydispersities.…”