Inorganic-organic functionally-graded films: The role of intermediate layers between TiO2 coatings and polymer substrates

Abstract

An organic/inorganic-graded film was fabricated by a loop-tail-train-like adsorption of polymer molecules on polymer materials. Silicon dioxide (SiO2)/polymethyl metacrylate(PMMA)-graded film of 50nm was fabricated by optimal fabrication conditions such as an inorganic/organic ratio of prepared polymer, a concentration of solvent and coating processes. The fabricated-graded film was applied as an intermediate layer between the photo-active TiO2 and the polymer. Sunshine weatherometer examination was conducted on the fabricated samples including the PMMA intermediate layer, the SiO2 intermediate layer prepared from tetraethoxysilane (TEOS), and the fabricated-graded layer. The strong oxidation power of photo-excited TiO2 deteriorated the PMMA/TiO2 interface resulting in a hazy appearance after the sunshine weatherometer test. Microcracks instead of deterioration by photo-oxidation were observed on the SiO2 intermediate layer after the sunshine weatherometer test, and these microcracks resulted in the hazy appearance of the film. The formation of cracks was attributable to the brittleness of the SiO2 intermediate layer. However, there was no change in appearance on the film utilising the SiO2/PMMA-graded intermediate layer.