Sol-gel synthesis of rodlike polysilsesquioxanes forming regular higher-ordered nanostructure

Abstract

Rodlike polysilsesquioxanes forming regular higher-ordered nanostructure such as hexagonal phase were prepared by sol-gel reaction of organotrimethoxysilanes having amino groups in aqueous solutions of inorganic strong acids. The XRD profiles of the resulting polysilsesquioxanes showed three peaks with the d-value ratio of 1 : 1/√3 : ½, indicating that these polysilsesquioxanes have hexagonal phase. The diffraction peaks shifted by changing the humidity. In addition, the d-values of diffraction peaks increased by ion-exchange reaction with organic compounds such as fatty acid salt and anionic polymer. Therefore, this hexagonal phase originated from the stacking of rodlike polysilsesquioxanes with Si–O–Si framework at the core and ammonium groups extruding outside. This Si–O–Si framework probably formed a ladder or ladder-related structure, which was characterized by solid-state 29Si NMR and IR spectrometries.