Aggregation behavior and adsorption properties of salt-free catanionic surfactant mixtures containing tetradecyltrimethyl ammonium salts

ABSTRACT

The aggregation behavior of salt-free catanionic surfactants, tetradecyltrimethyl ammonium hydroxide (TTAOH)/fatty acid (FA) including octanoic acid (OA), decylic acid (DA) and lauric acid (LA) in aqueous solutions were studied. The critical micelle concentration(cmc), surface tension at cmc (γ_cmc), surface excess (Г_max), mean molecular surface area (A_min), adsorption efficiency (pc₂₀) and surface tension reduction effectiveness (π_cmc) were obtained from surface tension isotherms. The influence of temperature on the surface tension of salt-free TTAOH/FA (TTAOF) systems was investigated. Data of adsorption dynamics indicated that at fixed adsorption time, the order of adsorption capacity was TTAOH < TTAOH/OA (TTAOO) < TTAOH/DA (TTAOD) < TTAOH/LA (TTAOL). The adsorption process of salt-free TTAOF was adsorption-controlled. The complex and storage moduli increased with increasing oscillation frequency, however, the loss modulus showed the opposite trend. The complex modulus passed through a maximum value with increasing concentration of salt-free surfactant TTAOF. The adsorbed TTAOF layer was elastic, and the elasticity increased with increasing hydrocarbon chain length of FA.

GRAPHICAL ABSTRACT

KEYWORDS:

• Anionic surfactants
• cationic surfactants
• interfacial science
• surface activity

Additional information

Funding

The authors acknowledge the financial support from National Natural Science Foundation of China (21306092 and 21376125), Science and Technology Plan Project of Shandong Provincial University (J12LA02), Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province.