Conformational Dynamics of Surfactant in a Mesolamellar Composite Studied by Local Field NMR Spectroscopy

Abstract

Ordered mesostructured materials possess unique surface, structural, and bulk properties that lead to important practical applications. Mesostructured organic–inorganic composites are also of broad interest for fundamental studies of confinement effects and surface interaction on structural and dynamic properties of organic molecules. In the present study, solid state dipolar 13C–1H NMR spectroscopy is applied to quantitatively characterize the conformational dynamics of a surfactant in a mesolamellar composite. By applying dipolar recoupling and separated local field spectroscopy techniques, the motion of surfactant molecules was studied in a wide range of mobilities from an essentially immobilized rigid state to a highly flexible and anistropically tumbling state. From the analysis of the measured heteronuclear dipolar couplings, the orientational order parameters of C–H bonds along the surfactant chain were determined. The study shows that in surfactant bilayers in AlPO layered structure at room temper...