Langmuir, Vol.13, No.25, 6618-6625, 1997
The Adsorption of Nonionic Surfactants in Hydrophilic Cylindrical Pores .2. Mean-Field Lattice Calculations
The adsorption behavior of nonionic surfactants in hydrophilic cylindrical pores has been studied with a mean field lattice (MFL) theory. The pore radius has two important influences on the adsorption isotherm. With decreasing radius (i) the adsorbed amount decreases and (ii) the step in the isotherm shifts to lower concentration. This behavior is rather generic. Neither the molecular architecture nor the adsorption energy influences these qualitative features. However, the position of the step in the isotherm becomes more sensitive to the curvature as the adsorption energy increases, just as has been predicted with the semithermodynamic (ST) theory. We have been partly successful in predicting the curvature behavior from the excess grand potential density profile of the flat adsorbed layer. All trends found with the full MFL calculations could be reproduced with the help of the curvature constants, calculated fr om the profile of the flat layer. However. the curvature constant was underestimated. At the step in the isotherm the error was about 25%.
Keywords:SILICA WATER INTERFACE;SOLID-LIQUID INTERFACE;FLUORESCENCE DECAY;ADSORBED LAYER;ASSOCIATION;GEL