Coupling selectivity in the radical-controlled oxidative polymerization of4-phenoxyphenol catalyzed by (1,4,7-triisopropyl-1,4,7-triazacyclononane)copper(ll) complex

Various effects on the coupling selectivity of the oxidative polymerization of 4-phenoxyphenol catalyzed by (1,4,7-triisopropyl-1,4,7-triazacyclononan e)copper(II) halogeno complex [Cu(tacn)X-2] are described. With respect to the amount of the catalyst and the nature of the halide ion (X) of Cu(tacn) X-2, the coupling selectivity hardly changed. The Cu(tacn) catalyst possess ed a turnover number greater than 1860. As the temperature of the reaction and the polarity of the reaction solvent were elevated, the C-O coupling at the o-position increased, but the C-C coupling was not involved. For the p olymerization in toluene at 80 degreesC, poly(1,4-phenylene oxide), obtaine d as a methanol-insoluble part, showed the highest number-average molecular weight of 4000 with a melting point (T-m) of 195 degreesC. Only a slight c hange in the coupling selectivity was observed in the presence or absence o f hindered amines as the base. Surprisingly, however, the C-O selectivity d ecreased from 100 to 24% with less hindered amines, indicating that the sel ectivity drastically changed from a preference for C-O coupling to a prefer ence for G-C coupling. (C) 2000 John Wiley & Sons, Inc.