Titania (TiO2) is an oxide commonly used for photocatalysis. This proclivity to form free radicals when exposed to light has also prompted interest in applying porous TiO2 as a reactive/responsive membrane. Surfaces of both main polymorphs of TiO2 (especially rutile {110} and anatase {101}) have been shown to be stable and photo-active.
Polyacrylic acid (PAA) is a molecule of interest as changes in pH can cause the molecule to contract or expand, due to changes in the charge distribution relating to the carboxyl group. Due to TiO2βs ability to generate photocarriers, we hypothesize that porous TiO2 substrates are able to induce light-mediated expansion/contraction in PAA. Photo-carriers from TiO2 modify charge distributions on PAA similar to how changes in pH have been shown to do
