The ionic polymerization of substituted o-quinodimethanes via thermal isomerization of benzocyclobutenes is described. In the cationic polymerizations of 1-methoxy-o-quinodimethane in the presence of various cationic initiators at 110 degrees C for 12 h, chain transfer reactions also considerably underwent besides the polymerization. Meanwhile, cationic polymerizations of 1-trimethylsilyloxy-o-quinodimethane under the same conditions gave good yields of the corresponding polymer. Anionic polymerizations of 1-cyano-o-quinodimethane in the presence of anionic initiators such as n-BuLi or t-BuOK were performed at various temperatures for 12 h. Good yields of hexane-insoluble polymer, which was produced by anionic polymerization of corresponding o-quinodimethane as an intermediate, were obtained above 120 degrees C. (C) 2007 Wiley Periodicals, Inc.