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Miyoko's Project Page - RISE summer 2003 |
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Intern: Miyoko Ohashi,
Mentor: Ryan Hayward
Faculty Supervisor: Brad Chmelka
Department: Chemical Engineering |
NANOSTRUCTURAL CONTROL OF SURFACTANT-SILICA THIN FILMS
Nanotechnology is an important field of study in recent years. One aspect
involves mesoporous materials, which contain pores in the 2-5 nm range.
Surfactants, molecules that possess two opposite polarity or charge, can form
complex structures at the nanometer scale level, including hexagonal, cubic and
lamellar liquid crystal phases. Liquid crystals formed by nonionic surfactants
can be fixed by allowing silica to solidify in the hydrophilic part of the
structure. Silica shaped around a liquid crystal can then be obtained by
burning out the organic component. The self-assembled structures can serve as
barriers, low dielectric or insulation materials, catalysts, and selective
membranes for separation processes. This research explores the production of
bicontinuous cubic silica nanostructures with Brij-56, a nonionic surfactant.
The large surface area and accessibility of pores makes the bicontinuous cubic
structure a promising candidate for catalysis. Also, the continuous network
of nanoporous structure may function as a selective membrane. This research
explores the phase structure diagram of the Brij-56/silicon dioxide system, in
comparison to the known phase diagram of the Brij-56/water system. The cubic
phase occupies a very small region of the surfactant/water phase diagram; yet
for applications in nanotechnology it is important that the desired structure
can be reliably produced. Thus, it is important to understand the control of
nanostructure by relevant parameters in order to optimize synthetic conditions.
Our results show that cubic structure forms around the same region of
composition and temperature in both systems. Further study is to be conducted
for deeper understanding of the behavior.
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