Two-Dimensional Sol−Gel Transition in Silica Alkoxides at the Air/Water Interface

Abstract

We have investigated the 2D viscoelastic behavior of the reactive sol-gel transition of silica alkoxides deposited at the air/acidic water interface of a Langmuir trough by oscillatory interfacial rheology. The storage and loss moduli increased with time as the hydrolysis-condensation reaction took place. There was evidence of a 2D gel point, which was discussed within the percolation theory framework. The power law dependence value of n=0.63 was similar to those found for bulk systems. The final network had a low fractal dimension value of df=1.17 (for a 2D system) indicating a rather open structure, in agreement with acidic catalysis, and a somewhat low effective modulus of 20 MPa.

Adsorption of microgels at an oil–water interface: correlation between packing and 2D elasticity

“…Moreover shear rheology is likely more adapted to detect the inuence of crosslinking. 52,53 A similar behaviour has also been reported for some proteins. For example, Freer and co-workers 54,55 studied extensively the hexadecane-water surface elasticity in presence of both a globular (lyzozyme) and a exible disordered protein (b-casein).…”

Dilatational rheology of a gel point network formed by nonionic soluble surfactants at the oil–water interface

“…This result was also observed, using dilatational rheology, with other very different systems such as the natural surfactant from petroleum oils, 9,10,13 but this is the rst time, to our knowledge, that interfacial gelation is reported with soluble surfactants unlike crude oil asphaltenes or insoluble monolayers spread at interfaces. [2][3][4][5][6][7][8] Similar gel point behaviors were obtained for all monolayers studied at C $ 0.033 g L À1 , each time exactly ful-lling eqn (1) and (2). Fig.…”

“…The formation of this two-dimensional gel depends on the chemical nature of the molecules and the gel can be formed only if the attractive intermolecular interactions are strong enough. To date, 2D gelation was only evidenced in literature with insoluble monolayers spread at the air-water interface, composed for instance of macromolecular systems like polymethyl methacrylate, 2 bcasein, 3 silica alkoxides 4 and polyethylene glycol lipopolymers. [5][6][7][8] In these reports, interfacial rheology experiments were performed with shear interfacial rheometers and thus the rheology measured was directly due to the relaxation of clusters with interfacial shear deformation at a constant area.…”