Dynamic surface properties of aqueous media imparted by a sugar-modified organosiloxane surfactant

Abstract

A novel tetrasiloxane-tailed surfactant bearing oligo(ethylene oxide) methyl ether and sugar moieties (TGA-2) has been evaluated. The dynamic surface tension (DST) and spreading properties imparted to water by TGA-2 have been investigated. DST parameters, namely effective diffusion coefficient, activation barrier, and contact angle have been calculated and analyzed. A general diffusion mechanism of surfactant TGA-2 has been delineated. DST analyses yielded significantly different long-term (DL) and short-term (DS) diffusion coefficients, implying that the adsorption process involves a mixed diffusion-kinetic mechanism. Adsorption activation energies (Ea) of the surfactant TGA-2 have been measured as 9.14 kJ/mol at 4 × 10−5 M and 19.37 kJ/mol at 4 × 10−4 M. These small Ea values suggest that the tetrasiloxane group is favorable for adsorption. A polytetrafluoroethylene (PTFE) membrane was chosen as a solid substrate to demonstrate the spreading ability imparted by TGA-2. At a TGA-2 concentration of 0.5% in water, the contact angle decreased from 57° to 7.8° in 60 s, such that the droplets became almost flat.