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Templates of a Supramolecular Block Copolymer for the Synthesis of
Ordered Nanostructured TiO<sub>2</sub> Films via Guest Exchange
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Abstract
In this work, we
introduce a facile method based on host–guest chemistry to
synthesize a range of nanostructured TiO<sub>2</sub> materials using
supramolecular templates of a dendron-jacketed block copolymer (DJBCP).
The DJBCP is composed of amphiphilic dendrons (4′-(3,4,5-tridodecyloxybenzoyloxy)benzoic
acid, TDB) selectively incorporated into a P4VP block of polystyrene-<i>block</i>-poly(4-vinylpyridine) (PS-<i>b</i>-P4VP) via hydrogen bonding. The PS-<i>b</i>-P4VP host
acts as a structure-directing template, while the guest molecules
(TDB) assist the self-assembly nanostructures and zone-axis alignment,
resulting in the nanostructured template of vertically oriented cylinders
formed via successive phase transformations from <i>Im</i>3̅<i>m</i> to <i>R</i>3̅<i>m</i> to <i>P</i>6<i>mm</i> upon thermal annealing
in the doctor-blade-cast film. The guest
molecules subsequently direct the titania precursors into the P4VP
domains of the templates via supramolecular guest exchange during
immersion of the film in a designated precursor solution containing
a P4VP-selective solvent. The subsequent UV irradiation step leads
to the formation of PS-<i>b</i>-P4VP/TiO<sub>2</sub> hybrids. Finally, removal of the host template by calcination leaves
behind mesoporous channels and makes sacrifices to be a carbon source
for carbon-doping TiO<sub>2</sub> materials. Various TiO<sub>2</sub> nanoarchitectures, namely, vertical and wiggly micrometer-length
channels, inverse opals, fingerprint-like channels, heterogeneous
multilayers, and nanotubes, have been fabricated by highly tunable
DJBCP nanostructures