Wettability of Polymethyl Methacrylate by Aqueous Solutions of Sodium Dodecyl Sulphate and Sodium Hexadecyl Sulphonate Mixtures

摘要

Contact angle meaurements were carried out with aqueous solutions of sodium dodecyl sulphate (SDS) and sodium hexadecyl sulphonate (SHS) mixtures on polymethyl methacrylate (PMMA) . From the results of these measurements and commbination of the Gibbs adsorption equation with Young's equation we calculated the ratio of the excess concentration of surfactants at the solid- solution interface to the excess of their concentration at the solution-air interface. From measurements and calculation it was found that were there were only small changes in the contact angles over the range of surfactant concentration in solution -air interface. However, if saturation of the surfactant layer is achieved then a considerable decrease in the contact angle as a function of concentration is observed. IT was also found that for all systems studied there is a straight linear relationship between adhesion tension and solution surface tension over the concentration range of the surfactants from O to concentration (c) close to the critical micelle concentration (c.m.c). The slope of the straight lines suggests that the concentration of the surfactants at the PMMA -solution interface is smaller that at the solution -air interface.