The oxidative coupling copolymerization between 2,6-dimethylphenol (DMP) and dihydroxynaphthalenes, such as the 2,3- and 2,6-dihydroxynaphthalenes (2,3- and 2,6-DHN), was carried out using a Cu catalyst under an O2 atmosphere. The polymerization was significantly affected by the structure of the comonomer, and the copolymers were efficiently obtained during the copolymerization of DMP and 2,6-DHN. The obtained copolymers containing hydroxyl groups of the DHN unit were further transformed into polymers containing ester and urethane groups. The obtained copolymers containing various functional groups showed a very different solubility from that of the homopolymer of DMP.

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The oxidative coupling copolymerization between 2,6-dimethylphenol (DMP) and phenols having various alkoxy groups, such as methyoxy (MOP), ethoxy, benzyloxy, butoxy, and 2-hydroxyethoxy groups, was carried out using a copper(II) catalyst under an O2 atmosphere. The copolymerizations with alkoxyphenols effectively proceeded, and the unit ratios of the obtained copolymers were in good agreement with those in the feed. The coupling regioselectivity, such as oxyphenylene (CO) and phenylene (CC), of the alkoxyphenol unit constructed during the copolymerization was also estimated by the 1 H NMR analysis of the acetylated polymer. As an example, the copolymer with the unit ratios of DMP:p-MOP = 50:50 and CO:CC = 67:33, was obtained in 71% yield during the copolymerization with p-MOP (feed ratio, 50:50) in a mixed solvent of CH2Cl2 and methanol (7/1 (v/v)) for 24 h. The solubility and thermal property of the obtained copolymers were significantly affected by the structure of alkoxyphenol unit. disubstituted phenols, such as 2-allyl-6-methylphenol and 2,6-diphenylphenol, as a comonomer [11][12][13][14]. Scheme 1: Active species for oxidative coupling polymerization of DMP.Scheme 2: Monomers used for copolymerization. Scheme 3: Oxidative coupling copolymerization between DMP and alkoxyphenols.