Interaction Forces between Glass Surfaces with Adsorption of Quaternary Trimeric Surfactants

Abstract

Interaction forces between glass surfaces with adsorption of quaternary trimeric ammonium surfactants have been studied using colloidal probe atomic force microscopy. The trimeric surfactants used are referred to as m-2-m-2m (m is the hydrocarbon chain length of each surfactant : 8,10, and 12). Dimeric (or gemini) 12-2-12 and monomeric dodecyltrimethylammonium bromide (DTAB) surfactants are also used for comparison. In the absence of the surfactants, the electric double layer repulsion was detected between the two glass surfaces. On the other hand, the force curve was dramatically changed by the addition of the surfactants : with increasing surfactant concentrations a repulsive-attractive-repulsive sequence of the surface forces was observed for 8-2-8-2-8 and 10-2-10-2-10, while the attractive concentration region was not seen for 12-2-12-2-12 adsorption. This difference is induced by the intermolecular strong affinity of 12-2-12-2-12 at the glass/solution interface. In addition, for a given alkyl chain length 12-2-12-2-12 shows a strong intermolecular association at the interface, comparing with 12-2-12 or DTAB. The obtained force results were well correlated with dispersion stability of corresponding silica suspensions.