Self-assembly and Rheological Properties of C12EO4and Aminosilane Mixtures

Abstract

Phase behavior, self-assembly, and rheological properties of 3-aminopropyltriethoxysilane (APTES) and nonionic surfactant, CH3(CH2)11(OCH2CH2)4OH (C12EO4), in water were studied. The self-assembled structures were determined by means of small angle X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), freeze-fracture TEM (FF-TEM), and 2 H nuclear magnetic resonance ( 2 H NMR) measurements and the properties of self-assembled mixtures were obtained by rheological measurements. With a variation of the composition, different self-assembled structures were ob- tained. In the Lα phase region, a phase structural transition from an aggregate with high curvatures to the lamellar structures with low curvatures is observed with an increase of APTES concentration at a constant concentration of C12EO4. At constant APTES concentration, with an increase of C12EO4 concentration, densely packed vesicles and planarly lamellar structures which behave the properties as gel-like solutions having the rather high viscosity coexist. The phase structural transition was considered to be induced by the insertion of the hydrolytic products of APTES into the palisade of the micelles of C12EO4. These new observations on phase structural transition and self-assembly of nonionic surfactant and aminosilane mixtures could be very important for the full understanding for their applications, especially as templates in the synthesis of silica ma- terials, etc. Keywords phase behavior; nonionic surfactant; aminosilane; rheological property; cryo-TEM