Head-to-head and head-to-tail multilayer n-alkylsilsesquioxane films

Two lamellar organosilica films made up of stacks of head-to-head and head-to-tail alkyl bilayers were synthesized by a UV-driven polymerization of n-C18H37SiCl3 and n-C18H37Si(OCH3)3, respectively. In addition to thermogravimetry and small-angle X-ray scattering, the characterization of these multilayer systems was focused on a variety of multinuclear solid-state NMR methods (1H, 29Si, 13C, 2D WISE). The chemical structure of the siloxane interlayer, the alkyl chain conformation and thermal stability were systematically investigated and compared. Through its marked sensitivity to molecular motion, solid-state NMR was used to investigate the effect of interdigitation on alkyl chain dynamics.