Concentration Profile of Polymer Solutions near a Solid Wall

Application of the evanescent-wave-induced fluorescence technique to the study of the interfacial depletion layer between a polymer solution and a solid barrier has yielded the first measurement of the monomer concentration as a function of the distance to the wall. The results have been obtained on a dilute aqueous solution of xanthan, a stiff polysaccharide of high molecular weight. The data are described quantitatively by an empirical model for semiflexible chains. Good agreement is also found with the Auvray model for fully rigid rods, for an equivalent rod length of $L=600\mathrm{}\pm 10$ nm.