Preparation of carboxylate group-containing rod-like polysilsesquioxane with hexagonally stacked structure by sol–gel reaction of 2-cyanoethyltriethoxysilane

Carboxylate group-containing rod-like polysilsesquioxane (PSQ-COO−Na+) with a hexagonally stacked structure was successfully prepared by the sol–gel reaction (hydrolytic polycondensation) of 2-cyanoethyltriethoxysilane (CETEOS) monomer in sodium hydroxide aqueous solution. The X-ray diffraction pattern of the cast film of PSQ-COO−Na+ showed three diffraction peaks with the d-value ratio of 1 : 1/√3 : 1/2, indicating the formation of hexagonal phase. In addition, the transmission electron microscopic image of PSQ-COO−Na+ showed a stripe pattern, indicating that the rod-like PSQs were stacked parallel. Self-organization of an ion pair composed of a carboxylate anion and a sodium cation, which was converted from the cyano group of CETEOS by hydrolysis under alkaline conditions, was a driving force for the formation of such regular higher-ordered structures of PSQ-COO−Na+.