Abstract
Water-soluble polymers comprising itaconic amide acid with acrylic acid or acrylamide, which contain carboxylic acid and amide groups capable of coordinating to the copper catalyst, were synthesized by radical polymerization using an azobisisobutyronitrile initiator. These polymers were used as polymer ligands to prepare copper complexes, which were subsequently analyzed by UV–Vis spectroscopy. The complexes were then used as catalysts for the oxidative polymerization of 2,6-dimethylphenol (DMP) to synthesize poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) under oxygen and in the presence of a surfactant in alkaline water. The polymerization conditions were optimized by varying the amounts of polymer ligands and copper precursors, the concentrations of surfactant and hydrogen chloride, and the temperature, resulting in PPO with a maximum yield of 93%, a number-average molecular weight (M n) of 3700, and a molecular weight distribution (M w/M n) of 2.12. This yield is higher than that previously achieved using arginine ligand in water (72%). Furthermore, the optimum conditions were applied in the copolymerization of DMP and 2-allyl-6-methylphenol to obtain a thermally crosslinkable copolymer in 95% yield (M n = 3000, M w/M n = 2.5). In addition, the catalyst complex of the copper–polymer ligand was recovered and reused after the polymerization of DMP. The catalyst maintained its activity even after being recycled five times, without the addition of copper precursor or polymer ligand, thereby demonstrating an environmentally friendly process wherein environmental emissions and production costs can be substantially reduced.
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The authors thank Frontier Research Center on Fundamental and Applied Sciences of Matters at National Tsing Hua University, Industrial Technology Research Institute, and Ministry of Science and Technology Taiwan (MOST) for financial support.
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Chen, HY., Lee, HW., Hua, SC. et al. Catalytic Cu(II)–polymer complexes as recyclable catalysts for the synthesis of poly(2,6-dimethyl-1,4-phenylene oxide)s in water. J Polym Res 23, 248 (2016). https://doi.org/10.1007/s10965-016-1147-6
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DOI: https://doi.org/10.1007/s10965-016-1147-6