Green Methodology with Ionic Liquids as a Media for Efficient Synthesis of Polyamides Derived from 4-(4-Dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione and Diacid Chlorides

Ionic liquids (ILs) represent a fascinating and potentially very valuable group of new solvents, which have the benefit of zero vapor pressure and therefore easier handling than many conventional solvents. They are attracting a lot of attention as volatile organic compound-free solvents, eco-friendly and green media. Room-temperature ionic liquids (RTILs) and particularly those based on substituted imidazolium cations, which can be synthesized easily from the commercially available starting material N-trimethylsilylimidazole and alkyl halides, are currently being extensively studied for a variety of applications. In this study a facile and efficient synthesis of heterocyclic polyamides by polycondensation of 4-(4-dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione with various commercially available aliphatic diacid chlorides in the presence of RTILs and molten tetrabutylammonium bromide as an IL was performed. The effect of various reaction parameters, including the nature of the ILs, the amount of IL, the reaction temperature, and the reaction time were investigated to optimize the conditions for the preparation of heterocyclic polyamides. The polymerization proceeded well in ILs without any catalyst and polyamides were obtained with high yields and moderate inherent viscosities. A comparative study between the effects exerted by different ILs and the conventional polymerization method is also reported.