Hexagonal-Structured Polysiloxane Material Prepared by Sol-Gel Reaction of Aminoalkyltrialkoxysilane without Using Surfactants

A higher-order nanostructured polysiloxane was prepared by the sol-gel reaction of 3-aminopropyltrimethoxysilane catalyzed by a strong acid such as hydrochloric acid or nitric acid. In the X-ray diffraction (XRD) profiles, this compound had three peaks: one prominent peak and two minor peaks. The d-value ratios of the three peaks were 1:1/ 3:1/2. This strongly indicates the formation of a hexagonal phase. The peaks shifted due to a change in the humidity and the resulting product was completely dispersed in water. In addition, the d-values of each peak of the anion-exchanged product changed while depending on the bulk of the counteranion. Such behaviors cannot be observed for hexagonal mesoporous silica. Therefore, we estimated that this hexagonal phase came from a stacking of rodlike polymer with Si-O-Si framework at the core and ammonium groups extruding outside. The transmission electron microscopy (TEM) images showed a stripe pattern, indicating that the rodlike polysiloxane had parallel stacking. The scanning electron microscopy (SEM) image showed that the aggregate of the polysiloxane lined up in a regular direction, suggesting that the nano-ordered rodlike structure influences the microordered regular structure. This rodlike polysiloxane with a hexagonal phase belongs to a new type of higher-ordered material, based on siloxane bonds.