Ionic liquids as novel solvents and catalysts for the direct polycondensation of N,N′-(4,4′-oxydiphthaloyl)bis-L-phenylalanine diacid with various aromatic diamines

Ionic liquids (ILs) are often considered green solvents capable of replacing traditional organic solvents and have been extensively studied in materials chemistry and catalysis. In this study, the direct polycondensation of N,N'-(4,4'-oxydiphthaloyl)-bis-L-phenylalanine diacid with various aromatic diamines was performed in IL media. The influence of various reaction parameters, including the nature of the IL cations and anions, the monomer structures, the reaction temperature, and the reaction time, on the yields and inherent viscosities of the resulting optically active poly(amide imide)s (PAIS) were investigated. Direct polycondensation successfully preceded in ILs and triphenyl phosphite (a condensing agent) without any additional extra components, such as LiCl and pyridine, which are used in similar reactions in ordinary molecular solvents. Therefore, ILs can act as both solvents and catalysts. Various high-molecular-weight, optically active PAIS were obtained in high yields with inherent viscosities ranging from 0.54 to 0.88 dL/g. This method was also compared with three other classical methods for the polycondensation of the aforementioned monomers. (c) 2005 Wiley Periodicals, Inc.