engleski

Modification of flat Ti/TiO2 surface with strong polyelectrolytes

Titanium is a widely employed material in the aerospace industry, biomedicine and dentistry due to the combination of favorable mechanical properties, great corrosion resistance and good tissue compatibility. Some of the titanium properties are attributed to the passive oxide layer, which spontaneously forms on the titanium surface in an oxygen-containing environment. The protective oxide layer, few nanometers thick, mainly consists of amorphous TiO2. Many properties of titanium can be improved by introducing polyelectrolyte films on its surface. For example, polyelectrolyte coatings offer a new way for antibacterial protection of titanium dental implants. Properties of such films are controlled by the interplay of various interactions between surface and adsorbed polymer molecules. A comprehensive understanding of these interactions may enable very fine-tuning of titanium surface properties. In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As a model polyelectrolytes, strongly charged polycation poly(diallyldimethylammonium chloride) (PDADMA) and strongly charged polyanion poly(sodium 4- styrenesulfonate) (PSS) were used. First, the bare titanium substrate was characterized by means of ellipsometry, atomic force microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. It was shown that the substrate surface is very flat with an average roughness of only 2.3 nm and oxide layer thickness of 3.8 nm. Furthermore, electrochemical measurements revealed a good corrosion resistance of Ti/TiO2 substrate. After the adsorption of polyelectrolytes, coated titanium surface was again examined using the above-mentioned methods. Enhanced anticorrosion characteristics were observed for surfaces fabricated by both polyelectrolyte films, while the surface roughness didn't significantly change. These results lead us to the conclusion that polyelectrolyte molecules form a stable nanofilm on Ti/TiO2 surface that partially or fully covers the surface. Our previous work made on the adsorption of PSS to rutile surface strongly corroborates these findings.

titanium/titanium dioxide surface ; polyelectrolytes ; ellipsometry, atomic force microscopy, cyclic voltammetry, electrochemical impedance spectroscopy

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