Live Templates of a Supramolecular Block Copolymer for the Synthesis of Ordered Nanostructured TiO₂ Films via Guest Exchange

Abstract

In this work, we introduce a facile method based on host–guest chemistry to synthesize a range of nanostructured TiO₂ 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/​TiO₂ hybrids. Finally, removal of the host template by calcination leaves behind mesoporous channels and makes sacrifices to be a carbon source for carbon-doping TiO₂ materials. Various TiO₂ 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