Polymerization of o-Quinodimethanes Bearing Electron-Donating Groups in Situ Formed by Thermal Isomerization of Benzocyclobutenes

The substituent effect on the polymerization of o -quinodimethanes generated by thermal isomerization of benzocyclobutenes and the reaction of the obtained polymer is described. Polymerizations of 1-methoxybenzocyclobutene ( 1 ), 1-acetoxy benzocyclobutene ( 2 ), 1-hydroxybenzocyclobutene ( 3 ), and 1-((trimethylsilyl)oxy)benzocyclobutene ( 4 ) as benzocyclobutenes bearing electron-donating groups were examined. Although polymerization of 2 and 3 did not afford any polymer, polymerization of 1 and 4 in the presence of a radical initiator gave MeOH-insoluble polymer ( M n = 5000−11000) in moderate yields at temperatures above 90 °C, respectively. The structures of the obtained polymers were confirmed to be ring-opened polymer ( 5, 6 ) by IR, 1 H-NMR, and 13 C-NMR. The yield of the polymer increased with increase of the concentration of the initiator. This polymerization was supported to proceed based on the driving force of aromatization stabilizing effect by semiempirical calculation. Radical copolymerizations of 1 with vinyl monomers were carried out to obtain the corresponding copolymers. Lastly, treatment of 3 with p -toluenesulfonic acid (10%) gave poly( o -phenylenevinylene) ( 7 ) quantitatively and its properties (UV absorption, T g, Td 10 (10% weight loss temperature)) were estimated.