Distributions of counterions on adsorption and aggregation behavior of Gemini quaternary ammonium salt

Abstract

The counterions had a particular influence on various physical and chemical properties, which were significantly present in Gemini quaternary ammonium salt. To investigate this contribution three Gemini quaternary ammonium salt with different counterions, GC-S, GC-N and GC-Cl, were synthesized from dodecyl tertiary amines, epichlorohydrin, and corresponding acids. The structures were characterized by FT-IR and 1H NMR. Critical parameters such as surface tension, minimum interfacial tension, CMC, and maximum adsorption capacity were measured subsequently. The role of counterions on the adsorption properties was discussed with the help of two classical adsorption models. Their aggregation behavior was observed by TEM. The results showed that counterions with larger ionic radii were adsorbed near the cationic head group more easily, which facilitates the arrangement of surface-active molecules by reduced the repulsive force between them on the adsorption layer. Moreover, the diversity of counterions allowed the surfactants to aggregate in solution to form micelles with different aggregation structures. Cationic surfactants with different counterions were studied as corrosion inhibitors, and found to exhibit temperature-dependent inhibition effects.