Rheological behavior of surfactant-based precursors of silica mesoporous materials.
The linear and non-linear viscoelastic behaviors of polymer-like micellar solutions of cetyltrimethylammonium tosilate (CTAT) with added NaOH and tetraethyl orthosilicate (TEOS) to produce precursors of mesoporous materials are studied. The effect of TEOS/CTAT (T/C) ratio at fixed CTAT concentration, CTAT concentration at fixed T/C and aging time are reported. The systems show increasingly larger deviations from near-Maxwell behavior upon increasing T/C ratio, CTAT concentration and aging. Moreover, in steady and unsteady shear-flow, shear banding develops between two critical shear rates, which tend to fade as the T/C ratio and aging increase. The Granek-Cates model is employed to analyze linear viscoelastic behavior. The Bautista-Manero-Puig (BMP) model is used here to reproduce the steady and transient nonlinear rheology of these systems. We explain these results in terms of the changes in inter-macromolecular interactions that arise out of the presence of colloidal additives in the viscoelastic gel. The ordered mesoporous materials were identified by X-ray diffractometry (XRD) and high-resolution transmission electron microscopy.
Mendoza
L D
LD
Departamento de Ingeniería Química, Universidad de Guadalajara, Boul. M. García-Barragán 1451, Guadalajara, Jal. 44430, México.
Rabelero
M
M
Escalante
J I
JI
Macías
E R
ER
González-Alvarez
A
A
Bautista
F
F
Soltero
J F A
JF
Puig
J E
JE