Bis(Diquaternary Ammonium)Salts: Synthesis, Effect of Spacer on Surface Activities and Aggregation Properties of Reactive Red 198 in Aqueous – Surfactants Solutions

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Abstract A series of bis-diquaternary ammonium salts (cationic Gemini surfactants) with different length in spacer were prepared and characterized. The surface properties such as the critical micelle concentration CMC, minimum surface tension γCMC, effectiveness of the surface tension reduction πCMC, maximum surface excess Γmax and surface area per molecule Amin have been determined by means of surface tension measurements. As expected, these surfactants have good surface activities than those conventional monomeric ones (dodecyl trimethyl ammonium chloride (DTAC)) and the spacer plays an important role in the surface properties. Under experimental conditions, surface parameters decreases with the increase of carbon number of the spacer the except analogue with a benzene ring due to its inflexibility. The aggregation ability of some practically used reactive azodyes (C.I. Reactive Red 198) in aqueous solutions and the prepared surfactants was investigated using UV-visible spectroscopic methods. The spectroscopic studies were extended in order to determine the effect of molecular structure of the surfactants on the aggregative properties of C.I. Reactive Red 198 (RR 198). The aggregation behaviour of the RR 198 in solutions and in the presence of additives is related to their apparent deviations from Beer's law and aggregation number (N). The aggregation constant (Kn) of the monomer/dimer equilibrium was calculated. The aggregate structures and the nature of the interacting pairs in this dye were discussed using Kasha exciton theory.