Sustainable atom transfer radical polymerization of methyl methacrylate (MMA) with activators generated by electron transfer (AGET ATRP) was done using microemulsion polymerization at the relatively low temperature of 30 °C. Ethyl 2-bromoisobutyrate (EBiB) was used as ATRP initiator, ascorbic acid (AA) was used as reducing agent, and CuCl2/N-bis(2-pyridylmethyl)octylamine (BPMOA) was used as catalyst. Microemulsion AGET ATRP of MMA was well-controlled, producing poly(methyl methacrylate) (PMMA) nanoparticles ∼5 nm in diameter and narrow molecular weight distributions (Mw/Mn = 1.20–1.40). After the polymerization and isolation of PMMA, the mixture containing catalysts and ILs was shown to be recoverable and recyclable. Upon replenishment of initiator, reducing agent, and monomer (MMA), AGET ATRP of MMA produced PMMA with reproducible molecular weights and narrow molecular weight distributions, even in the fifth cycle. Thus, this process was demonstrated as being sustainable. Furthermore, use of a new surfactant IL ligand, 3-{11-[(3-(bis(pyridin-2-ylmethyl)amino)propanoyl)oxy]undecyl}-1-methylimidazolium bromide (BPYP-[MIM]Br) or 3-{11-[(3-(bis(pyridin-2-ylmethyl)amino)propanoyl)-oxy]undecyl}-1-methylimidazolium hexafluorophosphorate (BPYP-[MIM]PF6), demonstrated rate-enhanced polymerization relative to the use of BPMOA as ligand, and good polydispersity (Mw/Mn = 1.20–1.50) of the resultant PMMA was maintained.
Imidazolium-type basic ionic liquids (BILs), including 1-butyl-3-methyl imidazolium hydroxide ([Bmim][OH]), 1-butyl-3-methyl imidazolium phosphate ([Bmim][PO4]), 1-butyl-3-methyl imidazolium carbonate ([Bmim][CO3]), and 1-butyl-3-methyl imidazolium bicarbonate ([Bmim][HCO3]), coordinated by iron chloride (FeCl3·6H2O), were used as both the ligand and catalyst in activators generated by the electron transfer ATRP (AGET ATRP) of methyl methacrylate (MMA) in bulk and solution, without the use of traditional ligands (such as 2,2-bipyridine, tetrabutylammonium bromide, and tetra-n-butylphosphonium bromide). Catalytic amounts of BILs could enhance the initiator efficiency (0.87–0.91) and the polymerization rate, and produce PMMA with controllable molecular weights and narrow molecular weight distributions (Mw/Mn = 1.20–1.40). The nature of the controlled/“living” free radical polymerization in the presence of BILs was confirmed by chain-extension experiments. The ready solubility and availability of BILs enable them to be applied as a new type of ligand and catalyst in iron-mediated AGET ATRP.
Plastic 1–14 pH indicator strips were prepared via cross-linking of an ionic liquid (IL) monomer, 1-butyl-3-vinylimidazolium bromide ([Bvim][Br]), with acrylonitrile, and followed by anion-exchange with anionic dyes. The resultant pH indicator strips exhibit enhanced pH-responsive colour changes and robust pH-response reversibility in both aqueous and organic solutions.
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