Advisor: K. Matyjaszewski.
The aim of the project is to explore the synthesis
of ordered mesoporous silicas using triblock copolymers
with three different blocks as micellar templates.
This is a largely unexplored area of research and
it may lead to the identification of new morphologies
of ordered mesoporous materials, as the phase
diagram of triblock copolymers with three different
blocks is more complex than that of block copolymers
with two different blocks, which have already been
extensively studied as templates for ordered mesoporous
silicas. The project will involve the synthesis
of triblock copolymers using commercially available
poly(ethylene oxide) homopolymers, which will be
block-extended by using atom transfer radical polymerization
(ATRP). The polymers will be characterized using
gel permeation chromatography and NMR. The resulting
block copolymers will be evaluated for the synthesis
of ordered mesoporous silicas in acidic aqueous
solution using tetraalkoxysilanes as silica sources. The
intended well-defined triblock copolymers will
have the following architecture: PEO-PX-PY,
where PEO is poly(ethylene oxide) and PX, PY are
two other blocks of different composition. PEO-PMA-PBA
(where PMA is poly(methyl acrylate), and PBA is
poly(butyl acrylate)) or PEO-PMA-PS (where PS is
polystyrene) are examples of potentially useful
triblock copolymers. For porous silica synthesis,
it is intended to use triblock copolymers
with 40 wt.% or more of hydrophilic PEO block,
because for higher contents of the hydrophobic
blocks, the solubility of the triblock copolymer
in water may be low, making the synthesis more
difficult. The block-copolymer-templated porous
silicas will be subsequently characterized using
small-angle X-ray scattering, thermogravimetry,
transmission electron microscopy and gas adsorption. |
