"Radical-controlled" oxidative polymerization of phenol (p-1) by (1,4,7-triisopropyl-1,4,7-triazacyclononane)copper(II) catalyst was performed and compared with that of 4-phenoxyphenol (p-2) in detail. Although the coupling selectivity for p-1 seemed to be controlled by the catalyst, the C-C coupling, which was excluded completely for p-2, occurred to some extent. The initial reaction rate of p-1 was much smaller than that of p-2, leading to the difference of polymerization behavior between p-1 and p-2. The rate-determining step would be the coupling of controlled radicals species from the ESR measurement of the reaction mixture. The polymer resulting from p-1 consisted mainly of phenylene oxide units, but had no crystallinity in contrast to the crystalline polymer from p-2. However, the present polymer showed the highest thermal stability in the polymers obtained by oxidative polymerization of p-1. (c) 2005 Wiley Periodicals, Inc.