Superhydrophobic TiO<sub>2</sub>–Polymer Nanocomposite
Surface with UV-Induced
Reversible Wettability and Self-Cleaning Properties
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Abstract
Multifunctional superhydrophobic
nanocomposite surfaces based on
photocatalytic materials, such as fluorosilane modified TiO<sub>2</sub>, have generated significant research interest. However, there are
two challenges to forming such multifunctional surfaces with stable
superhydrophobic properties: the photocatalytic oxidation of the hydrophobic
functional groups, which leads to the permanent loss of superhydrophobicity,
as well as the photoinduced reversible hydrolysis of the catalytic
particle surface. Herein, we report a simple and inexpensive template
lamination method to fabricate multifunctional TiO<sub>2</sub>–high-density
polyethylene (HDPE) nanocomposite surfaces exhibiting superhydrophobicity,
UV-induced reversible wettability, and self-cleaning properties. The
laminated surface possesses a hierarchical roughness spanning the
micro- to nanoscale range. This was achieved by using a wire mesh
template to emboss the HDPE surface creating an array of polymeric
posts while partially embedding untreated TiO<sub>2</sub> nanoparticles
selectively into the top surface of these features. The surface exhibits
excellent superhydrophobic properties immediately after lamination
without any chemical surface modification to the TiO<sub>2</sub> nanoparticles.
Exposure to UV light causes the surface to become hydrophilic. This
change in wettability can be reversed by heating the surface to restore
superhydrophobicity. The effect of TiO<sub>2</sub> nanoparticle surface
coverage and chemical composition on the mechanism and magnitude of
wettability changes was studied by EDX and XPS. In addition, the ability
of the surface to shed impacting water droplets as well as the ability
of such droplets to clean away particulate contaminants was demonstrated