Gelatin Adsorption at the Air/Water Interface As Investigated by X-ray Reflectivity

The method of X-ray reflectometry with electron density “labeling” of polyampholytes by heavy counterions has been demonstrated for measuring the adsorption profiles of gelatin at both hydrophobic (air/water) and like-charged hydrophilic (arachidic acid) surfaces. The results show that gelatin adsorbs onto a hydrophobic surface with a dense layer corresponding to the chain diameter, whereas this dense layer is absent for adsorption onto a hydrophilic like-charged surface. For both surface types a diffuse and extended adsorption layer is found.