Evanescent wave spectroscopy: Application to the study of the spatial distribution of charged groups on an adsorbed polyelectrolyte at the silica/water interface

Abstract

A new evanescent wave experimental technique with the capacity to determine simultaneously the spatial distribution of several chromophoric species located near a reflecting interface is reported. In a first step, to illustrate the capacity of this technique, the absorption of a model polyelectrolyte polymer (polyacrylamide/diacetone acrylamide copolymer grafted with an ionizable acridine chromophore) (EPI-26) onto the silica/aqueous solution interface has been studied. For this system, it has been demonstrated that variable angle of incidence evanescent wave spectroscopy may be used to determine quantitatively both the surface excess, Γ, and the mean separation distance from the interface z..