Polymerization of methyl methacrylate in the presence of iron(II) complex with tetradentate nitrogen ligands under conditions of atom transfer radical polymerization |
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Authors: | Khalid Ibrahim Katariina Yliheikkilä Barbro Löfgren Markku Leskelä Jukka Seppälä |
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Institution: | a Laboratory of Polymer Technology, Department of Chemical Technology, Helsinki University of Technology, P.O. Box 6100, FIN-02015 HUT, Finland b Laboratory of Inorganic Chemistry, Department of Chemistry, University of Helsinki, P.O. Box 55, FIN-0004 Helsinki, Finland c Department of Chemistry, Hashemite University, P.O. Box 150459, Zerqa 13115, Jordan |
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Abstract: | Four tetradentate nitrogen ligands, viz. dichloro{N,N′-diphenyl-N,N′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (1), {N,N′-dioctyl-N,N′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (2), {N,N′-dibenzyl-N,N′-di(quinoline-2-methyl)]-1,2-ethylene diamine} (3), and (1R,2R)-(−)-N,N′-di(quinoline-2-methyl) di-iminocyclohexane (4), were investigated as novel complexing ligands in iron-mediated atom transfer radical polymerization (ATRP) of methyl methacrylate where ethyl-2-bromoisobutyrate was the initiator in o-xylene at 90 °C. With ligands 1 and 2 the experimental molecular weights increased gradually with monomer conversion. High to moderate conversions (87%, 43%) were obtained in relatively short times (90 min for 1 and 30 min for 2), which indicates an efficient catalyst system, but after these times a dramatic increase in viscosity of the polymerization medium led to loss of control. It is noteworthy that polymerization proceeded in a controlled manner with ligand 1, which has two rather bulky substituents on the N-atom. Such bulky ligands did not work for a copper-based system, where they led to excessive terminations or other side reactions. When the bulkiness of the substituents was significantly increased, as in ligand 3, a decrease in polymerization rate and loss of control occurred. Ligand 4 was less efficient than the other ligands, probably because the ethylene bridge was replaced by cyclohexane bridge. |
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Keywords: | ATRP Controlled free radical polymerization Methyl methacrylate Bulkiness Deactivation Chain transfer agent |
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