The oxidative coupling polymerization of o-cresol was investigated using various 2-substituted pyridine/CuCl catalysts under an oxygen atmosphere, in which 2-phenylpyridine/CuCl and 2-(p-tolyl)pyridine/CuCl catalysts yielded poly(o-cresol)s with higher regioselectivity for 1,4-coupling. These polymerizations produced branched and crosslinked polymers in the later stages of polymerization. These polymers showed good thermal properties, such as 5% weight loss temperatures of up to 406 degrees C and glass transition temperatures of up to 151 degrees C. (c) 2019 Wiley Periodicals, Inc.