NMR Methods for Studies of Organic Adsorption Layers

Abstract

This chapter provides an overview of the possibilities to apply nuclear magnetic resonance (NMR) methods in the investigation of organic adsorption layers at solid interfaces, focussing on adsorption from aqueous solutions. In adsorption studies of compounds such as surfactants, polymers or lipids, standard methods of investigation are for example optical reflection techniques, infrared spectroscopy, and X-ray or neutron reflectivity. These reveal pure structural parameters such as layer thickness, adsorbed amount, surface roughness or molecular orientations. The variety of local dynamic information achievable from various NMR methods makes it an especially attractive goal to apply magnetic resonance techniques to interfaces as well, however, with a low sensitivity and motional aspects as the main limitations, investigations of large organic molecules in interaction with interfaces have been rare for a long time. The most important task in NMR adsorption layer studies is to choose suitable methods according to the system under investigation, and the underlying principles and basics of NMR are described in the chapter. Aimed at experimentalists in the field of organic adsorption layers, the purpose is to provide an overview of the current possibilities and achievements of NMR in surfactant, lipid, and polymer films. The focus is on methodological aspects to clarify the question of applicability of different kinds of NMR techniques in dependence on the widely varying conditions in different classes of adsorption layers. The chapter is limited to the field of NMR applications to interfaces, which form model systems for layers at planar solid/liquid interfaces. The focus is on colloidal templates as substrates for adsorption from aqueous solution.