Abstract
Highly active catalyst systems for polymerizing 2,6-dimethylphenol were studied by using aromatic amine ligands and copper(I) chloride. The aromatic amine ligands employed were pyridine, 1-methylimidazole, 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine. A mixture of chloroform and methanol (9:1, v/v) was used as a polymerization solvent. All experiments were performed with oxygen uptake measurement apparatus, while the reaction rate for each aromatic amine ligand-Cu catalyst system and the amount of by-product, 3,3′,5,5′-Tetramethyl-4,4′diphenoquinone (DPQ), were measured to determine the efficiency of the catalyst systems. The 4-aminopyridine/Cu (I) catalyst system was found to be extremely efficient in poly(2,6-dimethyl-1,4-phenylene ether) (PPE) synthesis; it had the fastest reaction rate of 6.98 × 10−4 mol/L·s and the lowest DPQ production. The relatively high basicity of 4-aminopyridne and the less steric hindrance arising from a coordination of Cu and 4-aminopyridine in this catalyst are responsible for the fast polymerization rate. When 2-aminoprydine (an isomer of 4-aminopyridine) was used as a ligand, however, no polymerization occurred probably due to steric hindrance.
Highlights
Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is one of the most important engineering plastics, with a unique combination of mechanical properties, low moisture absorption, an excellent electrical insulation property, dimension stability, and inherent flame resistance [1]
L3 resulted in higher molecular weights than the other ligands probably because it is an effective ligand leading to a fast reaction rate and the basicity was not too large, so catalyst poisoning did not occur until the end of the reaction
PPE was synthesized under three conditions with various aromatic amine ligands, including 1-methylimidazole, which is widely used for PPE synthesis
Summary
Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) is one of the most important engineering plastics, with a unique combination of mechanical properties, low moisture absorption, an excellent electrical insulation property, dimension stability, and inherent flame resistance [1]. PPE remaining DPQ a detrimental rolerole thatthat accelerates the decomposition of PPEofwhile while processing it at high temperature. PPE andof change theand color, especially whenespecially aliphatic when amine areverified used. This was verified by 13C-NMR spectroscopic analysis, and amine aliphatic ligands are used.ligands. Considering the mentioned aspects, different types of aromatic ligands were employed employed in instead this study instead ofamine, aliphatic amine, which can bein contained in to a polymer, to aim for in this study of aliphatic which can be contained a polymer, aim for developing developing a highly active aromatic amine/Cu catalyst system with a fast reaction rate and that in is a highly active aromatic amine/Cu catalyst system with a fast reaction rate and that is low low DPQ production
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