Synthesis of thermally stable polyamides with pendant 1,3,4-oxadiazole units via direct polycondensation in ionic liquids

The synthesis of high molecular weight polyamides by using 1-methyl-3-alkyl imidazolium bromides (alkyl = C3–C8) as reaction media has been reported. Polymers were prepared from the reaction of 2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine, POBD, and aromatic/aliphatic dicarboxylic acids in ionic liquids in the presence of triphenyl phosphite as a condensing agent without requiring any extra components such as CaCl2 or pyridine. The number average molecular weight of the polymers was measured by vapor pressure osmometry. The effects of various reaction parameters such as alkyl chain length of ionic liquids, reaction temperature, and reaction time on the molecular weight were investigated. No regular relationship between inherent viscosity or molecular weight with the alkyl chain length in the ionic liquid was observed; however, the highest molecular weight was observed in 1-butyl-3-methyl imidazolium bromide. The thermal properties of the prepared polymers were also studied with DSC and TGA methods. Removal of Co2+ from aqueous solutions was performed using polymer (7).