Atom transfer radical polymerization of acrylates in an ionic liquid: Synthesis of block copolymers

Abstract

Atom transfer radical polymerization (ATRP) of acrylates in ionic liquid, 1-butyl-3-methylimidazolium hexaflurophospate, with the CuBr/CuBr 2 /amine catalytic system was investigated. Sequential polymerization was performed by synthesizing AB block copolymers. Polymerization of butyl acrylate (monomer that is only partly soluble in an ionic liquid forming a two-phase system) proceeded to practically quantitative conversion. If the second monomer (methyl acrylate) is added at this stage, polymerization proceeds, and block copolymer formed is essentially free of homopolymer according to size exclusion chromatographic analysis. The number-average molecular weight of the copolymer is slightly higher than calculated, but the molecular weight distribution is low (M w /M n ϭ 1.12). If, however, methyl acrylate (monomer that is soluble in an ionic liquid) is polymerized at the first stage, then butyl acrylate in the second-stage situation is different. Block copolymer free of homopolymer of the first block (with M w /M n ϭ 1.13) may be obtained only if the conversion of methyl acrylate at the stage when second monomer is added is not higher than 70%. Matrix-assisted laser desorption/ionization time-of-flight analysis confirmed that irreversible deactivation of growing macromolecules is significant for methyl acrylate polymerization at a monomer conversion above 70%, whereas it is still not significant for butyl acrylate even at practically quantitative conversion. These results show that ATRP of butyl acrylate in ionic liquid followed by addition of a second acrylate monomer allows the clean synthesis of block copolymers by one-pot sequential polymerization even if the first stage is carried out to complete conversion of butyl acrylate.

Copper(0)-mediated radical polymerisation in a self-generating biphasic system

“…5, 22,23 A range of methods has been reported which keeps the catalyst insoluble in the polymerisation phase including the use of fluorous biphase systems, [24][25][26][27] supported catalysts [28][29][30][31] and ionic liquids. [32][33][34][35] A solid supported catalyst can be easily removed, 36,37 but diffusion of reactants to the catalytic site can present a problem. 38, 39 One of us has also explored the use of [N-alkyl-(2-pyridyl)methanimine]copper(I) complexes which had tuneable solubility in certain organic solvents used in this type of polymerisation.…”

“Green” Atom Transfer Radical Polymerization: From Process Design to Preparation of Well-Defined Environmentally Friendly Polymeric Materials

“…390 Acrylates were also polymerized successfully in ionic liquids, 391 and the preparation of block copolymers was reported as well. 392 ATRP of acrylates was carried out in chiral ionic liquids, and it was shown that the chirality of the medium affected, although not significantly, the tacticity of the produced polymers. 393 Both copper-and iron-mediated ATRP could be conducted in ionic liquids; in the latter case, no extra ligands were needed to achieve controlled polymerization.…”

Chain transfer to ionic liquid in an anionic polymerization of methyl methacrylate

“…[1][2][3] Ionic liquids are organic salts that are liquid at ambient temperatures, containing most commonly ammonium or phosphonium cations and various anions such as simple halide or complex anions (e.g., BF Application of ionic liquids as solvents for radical polymerization, including controlled radical polymerization, has been studied most extensively and some beneficial effects, such as increase of the ratio of propagation to termination rate constants (k p /k t ) leading to improved control in e.g., ATRP of (meth)acrylates have been observed. 4,5 There are also reports on the application of ionic liquids as solvents for cationic polymerization 6,7 but anionic polymerization in ionic liquids has not been reported till now, although in one paper Group Transfer Polymerization (GTP) of methyl methacrylate (MMA) has been described. 8 Anionic polymerization of some vinyl monomers, as shown originally by Szwarc, may proceed as a living process.…”