Solute exclusion and potential distribution near hydrophilic surfaces

Abstract

Long-range interaction between polymeric surfaces and charged solutes in aqueous solution were observed microscopically. At low ionic strength, solutes were excluded from zones on the order of several hundred microns from the surface. Solutes ranged in size from single molecules up to colloidal polystyrene particles 2 UPmum in diameter. The unexpectedly large exclusion zones regularly observed seem to contradict classical DLVO theory, which predicts only nanometer-scale effects arising from the presence of the surface. Using tapered glass microelectrodes similar to those employed for cell-biological investigations, we also measured electrical potentials as a function of distance from the polymeric surface. Large negative potentials were observed - on the order of 100 mV or more - and these potentials diminished with distance from the surface with a space constant on the order of hundreds of microns. The relation between potential distribution and solute exclusion is discussed © 2006 Springer.