The Study Of The Surface Adsorption Of The Novel Alkanolamides In Aqueous Solution

The three novel alkanolamide derivatives, such as N-(2-(2-hydroxyethoxy)ethyl) dodecanamide (QL-1) and N-(2-(2-hydroxyethoxy)ethyl)decanamide (QL-2) and N-(2-(2-hyd roxyethoxy)ethyl)octanamide(QL-3), were synthesized. And their structures were characterized by IR and NMR. The equilibrium surface tension and dynamic surface tension of QL-1 and QL-2 and QL-3 were measured by the ring method and the maximum bubble pressure method, respectively. The effects of temperature, concentration, and salt on the adsorption energies of QL-1, QL-2 and QL-3 had been investigated systematically. According to the Word-Tordai equation, the effective diffusion coefficient Da and the adsorption barrier Ea were obtained.The critical micelle concentrations (CMCs) of QL-1, QL-2 and QL-3 were 0.29, 3.92 and39.50 mmol/L at 303.15 K, respectively. The surface tensions of QL-1, QL-2 and QL-3 at CMC were 29.5, 28.9 and 30.8 mN/m, respectively. The saturated extent of adsorption of QL-1 and QL-2 were 3.6 and 4.4μmol/L, respectively. The critical micelle concentration of QL-1 is lower than that of QL-2 due to the longer hydrophobic chain. There was little influence on the surface tension, the CMC and the saturation adsorb quantity of QL-1 and QL-2 by the addition of salts.The diffuse coefficient of QL-1, QL-2 and QL-3 were measured at different concentration and temperature. The adsorption process is controlled by a diffusion step at short time, and it changes to a mixed kinetic diffusion adsorption mechanism at long time. As temperature increase, the speed of molecule was faster. When the concentration was higher, the adsorption barrier was bigger. The adsorption barrier of QL-1 at 0.10 and 0.20 mmol/L were 48.97 and 37.50 kJ/mol, respectively. Moreover, the addition of salt resulted in the short balance time. The adsorption process is controlled of QL-3 at short time and long time.