X-ray scattering experiments on sputtered titanium dioxide coatings onto PVDF polymers for self-cleaning applications

Abstract

The performance of active polymer substrates used in sensor and actuator or tactile display applications can be hindered by the inevitable soiling of their surface. A possible approach to overcome this problem is to deposit a self-cleaning coating onto the polymer surface, taking care that the layer underneath withholds its intrinsic properties. In this work, titanium dioxide, TiO2, was naturally chosen for coating material due to its inherent photocatalytic properties. Thus, TiO2 thin films were deposited by reactive magnetron sputtering on poly(vinilydene fluoride) - (PVDF) substrates, in its a- (nonelectroactive) and b- (electroactive) phases. Wide angle x-ray scattering (WAXS) experiments in a synchrotron were performed to monitor the crystalline structure of the polymer substrates upon thin film deposition and also to assess the crystalline structure of the TiO2 coating at different temperatures. In the WAXS patterns of the coated a-PVDF, the TiO2 polymorph anatase phase can be distinguished. At the same time, no explicit diffraction peaks for anatase were detected in the coated b-PVDF. Fourier transform infrared spectroscopy evidenced that the chemical structure of PVDF is unaffected by the coating deposition process. These structural results have been correlated with the photocatalytic properties of the TiO2 coatings.