ADSORPTION OF (GAMMA-AMINOPROPYL)TRIETHOXYSILANE AND RELATED MOLECULES AT THE SILICA HEPTANE INTERFACE/

(gamma-Aminopropyl)triethoxysilane (APTES) and simpler molecules havin g at least one common function with APTES (i.e., propylamine and mono- , di-, or triethoxyalkylsilane) were adsorbed at the silica/heptane in terface at 25 degrees C. The hydrolysis of ethoxy functions by surface water is observed only for APTES, which stresses the catalytic effect of the amine function. When the water surface content of silica is de creased by a heat treatment, a decrease of both APTES surface concentr ation and adsorption enthalpy is observed, whereas they increase in th e case of propylamine. This behavior is close to that observed in the case of triethylsilanol adsorption on silica which is interpreted as a n enhancement of siloxane bond formation by surface water.