Effects of HPC on the microstructure and hydrophilicity of sol–gel-derived TiO2 films

Sol–gel-derived titanium dioxide (TiO2) coating films were prepared with various amount of hydroxypropylcellulose (HPC) as additive. The formation mechanism of HPC-modified TiO2 films was studied by FTIR analysis of the sols. It was revealed that HPC anchors on the surface of TiO2 colloid. The action between the polymers decides the distribution of TiO2 colloid in the sol. Transmission electrical microscopy (TEM) and scanning electrical microscopy (SEM) showed that the particle size of TiO2 decreased and the microstructure of the film became loose with the addition of HPC, reaching an optimum when the concentration of HPC was 4.5×10−3 g/g sol. Further addition of HPC made the microstructure became dense. The photo-induced hydropholicity and the photocatalytic activity of the films were evaluated. The film showed good self-cleaning ability when the concentration of HPC was 4.5×10−3 g/g sol, which can be ascribed to its uniform less agglomerated microstructure.