Sol–Gel Preparation of Amphiphilic Silsesquioxane Containing Ether-Chain and Ammonium Groups Capable of Forming Reverse Micelles

In this study, we prepared an amphiphilic silsesquioxane (Am-SQ) capable of forming reverse micelles. The synthesis was performed by the sol–gel reaction of a mixture of triethoxysilane containing an ether-chain and 3-aminopropyltrimethoxysilane in aqueous hydrochloric acid. The gel permeation chromatography measurement of Am-SQ in chloroform eluent (<1.0 w/v%) showed a correlation between the excluded volumes (molecular weights of the peak tops; M_p’s) and concentrations, i.e., higher M_p’s at higher concentrations. On the contrary, the M_p’s of Am-SQ in chloroform were constant at concentrations above 1.0 w/v%. These results indicated that Am-SQ could form reverse micelles at a relatively high concentration in chloroform. Furthermore, dynamic light scattering measurements of the Am-SQ chloroform solutions having various concentrations were performed. The average particle size (diameter) of the 0.5 w/v% Am-SQ solution was assessed to be 0.86 ± 0.13 nm, whereas those in the solutions above 1.0 w/v% concentration were 8–11 nm, indicating that Am-SQ afforded stable reverse micelles at concentrations above 1.0 w/v%. In addition, the reverse micelles of Am-SQ in chloroform could incorporate ionic hydrophilic dyes, such as tetraphenylporphine tetrasulfonic acid and 1,3,6,8-pyrenetetrasulfonic acid tetrasodium salt, as confirmed both visually and by UV-Vis spectroscopy.