Functionalized aluminum oxide by immobilization of totally organic aromatic polymer spherical nanoparticles

Abstract

A novel surface protection method of anodic aluminum oxide (AAO) was developed by using a one-pot, one-step reaction with two environmentally friendly pure organic materials. Totally organic aromatic polymer spherical nanoparticles (SNPs) were immobilized on an AAO surface with one-step addition condensation and polymerization using monomers of 1,5-dihydroxynaphthalene and hexamethylenetetramine. Immobilizing the nanoparticles—with a maximum size of approximately 50 nm—on the scale-like structure provided high water-repellency with a maximum contact angle of 118.4°. The water-repellency arose from the Lotus effect. In addition, immobilization of SNPs induced anticorrosivity against acid and an increase of the withstanding voltage by 18.1%. This immobilization technique of SNPs on the AAO could be used as an effective chemical protection method for an AAO substrate. It was demonstrated that SNPs were chemically bonded to AAO. A cross-section of the AAO with the immobilized SNPs was also investigated. The cross-section was a hierarchical structure comprising four kinds of layers (nanoparticle layer, scale-like and reticular layer, sealed layer of AAO, and AAO layer). Immobilization of SNPs on the surface of AAO provided an excellent anticorrosion effect and a higher electric strength compared with that of unmodified AAO.