Synthesis and characterization of methoxybenzene-linked polyimides formed by 1,4-addition to bismaleimides

Abstract

Methoxybenzene-linked polyimides were synthesized by a trifluoromethanesulfonic acid (TfOH)-catalyzed 1,4-addition (Michael addition) reaction. Newly synthesized 1,3-bis(3,5-dimethoxyphenoxy)propane and known 5,5′-oxybis(1,3-dimethoxybenzene) as nucleophilic monomers were reacted with several bismaleimides in the presence of a catalytic amount of TfOH in m-cresol. Use of 1,3-bis(3,5-dimethoxyphenoxy)propane afforded polyimides with number average molecular weights (Mn)s of 8000–15000. However, polyimides with Mn of 4000 or less were obtained when 5,5′-oxybis(1,3-dimethoxybenzene) was employed as a monomer. The synthesized polyimides showed good thermostability as judged by 10% weight loss temperatures between 417 and 441 °C. Their glass transition temperatures were around 200 °C. These polymers featured a wide range of solubility in organic solvents such as m-cresol, DMF, pyridine, and chloroform.