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

摘要

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 (D-L) and short-term (D-S) diffusion coefficients, implying that the adsorption process involves a mixed diffusion-kinetic mechanism. Adsorption activation energies (E-a) of the surfactant TGA-2 have been measured as 9.14 kJ/mol at 4 x 10(-5) M and 19.37 kJ/mol at 4 x 10(-4) M. These small E-a 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 degrees to 7.8 degrees in 60 s, such that the droplets became almost flat.