IN SITU SYNCHROTRON SAXS STUDY OF THE FORMATION OF MCM-41 AND MCM-50
Patrik Agren1, Mika Lindén1, Jarl B. Rosenholm1, Robert Schwarzenbacher2, Manfred Kriechbaum2, Heinz Amenitsch2, Peter Laggner2, Juliette Blanchard3 and Ferdi Schüth3
1Dept. of Physical Chemistry, Abo Akademi
University, Porthaninkatu 3-5, FIN-20500 Turku, Finland
2Institute of
Biophysics and X-Ray Structure Research, Austrian Academy of
Sciences, Steyrergasse 17/VI, A-8010 Graz, Austria
3Dept. of Inorganic and Analytical
Chemistry, Johann Wolfgang Goethe Universität, Marie Curie Str.
11, D-60439 Frankfurt am Main, Germany
The formation of hexagonal and lamellar surfactant-silicate
mesophases at room temperature has been investigated by in
situ synchrotron small angle X-ray scattering. Following
chemicals were used in the experiments: water, ammonia, TEOS,
CTAB, butanol and hexanol. Emphasis was given to the influence of
butanol and hexanol on the surfactant-silicate phase behavior.
The X-ray measurements were performed at the Austrian high flux
SAXS beamline of the 2 GeV electron storage ring ELETTRA,
Trieste, Italy The experimental setup included a continuos flow
reactor allowing a resolution in time as high as 0.3s, which
allowed detailed information about the initial stages of
silicate-surfactant mesophase formation. Depending on the
reaction composition, one, two or three co-existing phases were
observed. Furthermore, the observed structures were hexagonal or
lamellar or a mixture of both phases. The results are discussed
in terms of time-dependent changes in the concentration of
co-surfactant not incorporated into the composite aggregates.
Although many of the observed effects are paralleled by well
known properties of aqueous surfactant solutions, important
dissimilarities exist. Furthermore, the relative intensity of the
high-order reflexions are suggested to correspond to the degree
of inter-aggregate condensation in the composite mesophase.