Structuring of di-alkyl-urethanesils

A novel organized di-urethane crossed-linked dodecyl/siloxane (di-alkyl-urethanesil) was synthesized by the sol–gel process and self-directed assembly, from the organosilane precursor (CH3CH2O)3-Si-(CH2)3-NHC( = O)O-(CH2)12-O(O = C)NH-(CH2)3-Si-(OCH2CH3)3, through a fine control of the reaction conditions (hyper-stoichiometric amount of water, minor amount of tetrahydrofuran, and acid catalysis; molar ratio Si:H2O:HCl:THF = 1:300:0.1:12.5). The new bridged silsesquioxane was identified by the notation d-Ut(CY)AC, where Y = 12 is the number of carbon atoms C of the bridging alkyl chains and AC represents acid catalysis. The d-Ut(C12)AC material exhibits a structured lamellar organization with medium long-range order, a texture composed of homogeneous lamellae immersed in a sponge-like matrix made of randomly distributed thin plates, and is thermally stable up to ca. 350 °C. Despite the hydrophobic nature of the dodecane chains, the weakness of the urethane–urethane hydrogen-bonded array formed led to the growth of moderately ordered assemblies of amphiphilic organo(bis-silanetriol) substructures comprising mainly all-trans conformers.