Dynamics of methylene chains in an intercalated surfactant bilayer by solid-state NMR spectroscopy

Two complementary solid-state NMR techniques – variable contact time cross-polarization magic angle spinning (VCT CPMAS) and 2D wide-line separation (2D WISE) spectroscopy have been used to probe the dynamics of methylene chains in an intercalated surfactant bilayer, formed within the galleries of layered cadmium thiophosphate by the insertion of cetyl trimethyl ammonium ions. A gradient of conformational mobilities is observed in the intercalated bilayer; the cationic heads are immobile while the terminal methylenes of the surfactant tail undergo rapid motion. In the crystalline salt, the gradient is reversed, the tails are stationary and the heads mobile.