THE ADSORPTION OF n-OCTADECYLAMINE, n-OCTADECANOIC ACID, AND n-OCTADECYL ALCOHOL FROM NONAQUEOUS SOLUTION ONTO HYDRATED AND DEHYDRATED METAL 0X1DE SURFACES

摘要

A study has been made of the adsorption of the normal C18 amine, acid, and alcohol from hydrocarbon solution onto freshly polished stainless steel, iron, nickel, chromium, and platinum surfaces as a function of substrate pretreatment. The pretreatment consisted of maintaining the polished surface for 3 hours in a helium or air environment at selected temperatures ranging from ambient to 320 °C. Isolation of the monolayer-covered surface was accomplished by the method of retraction, and the degree of coverage was determined by measuring the contact angle. Treatment of the metal surface at temperatures from 25 to 200°C resulted in a more-or-less continuous decline in ability to adsorb a close-packed monolayer of the amine. Above 200°C, however, amine adsorption in¬creased with increasing pretreatment temperature except on platinum. The re¬gain in amine adsorption is believed to be connected with oxide film growth.nIn anhydrous solution neither the alcohol nor the acid formed a close-packed monolayer. On the other hand, it was possible to obtain a monolayer and even crystallites of octadecanoic acid when the substrate was heavily hydrated and the adsorbaté solution was saturated with water.