Adhesion of organics to the native oxide surfaces of titanium and titanium-6 aluminum-4 vanadium alloy.

摘要

Titanium and Ti alloys are commonly used structural materials in aerospace design, architecture, and importantly, biomedical applications, in part due to the stability or non-reactivity of their native oxide surfaces, which protects them from corrosion. However, the non-reactivity of these surfaces makes it difficult to attach paints, coatings, or, in the context of biomedical implants, bone. Three methods are described herein which were developed to enable the covalent attachment of organics to the native oxide surfaces of titanium and titanium-6 aluminum-4 vanadium alloy (Ti-6Al-4V). The first method involves the adhesion of alkylphosphonic acids directly to the native oxide surfaces of titanium and Ti-6Al-4V by aerosol deposition, followed by gentle heating. Infrared (IR) reflectance spectroscopy, wetting contact angle measurements and atomic force microscopy (AFM) showed an ordered monolayer of long alkyl chains organized on the surface in large domains. The second method utilizes a stable titanium(III) phosphate interface to attach alkylthiols, amines, and ethoxysilanes to the native oxide surfaces of titanium and Ti-6Al-4V. X-ray diffraction, profilometry and AFM were used to characterize the interface; IR reflectance spectroscopy and wetting contact angle measurements showed a disordered, but comprehensive, organic film covering the surface. The third method involves the attachment of thiols, carboxylic acids, and phosphonic acids to the native oxide surfaces of titanium and Ti-6Al-4V through a covalent network of bonds and a zirconium complex interface. IR reflectance spectroscopy, X-ray photoelectron spectroscopy and wetting contact angle measurements gave the order and stoichiometry of the interfacial complex and organic film.; Fibroblast cell adhesion studies were conducted on: methyl-, hydroxyl-, carboxylic acid-, and RGDC-terminated phosphonoalkyl chains attached to the native oxide of titanium; and amine- and RGDC-terminated alkylsilanes attached to the native oxide of titanium through the Ti(III) phosphate interface. The fibroblasts adhered to and spread on the RGDC-terminated samples and the foils coated simply with Ti(III) phosphate, but they did not adhere to or spread on the native oxide surface of titanium.