Fractal Materials and Their Functional Properties

Abstract

Fractal, a mathematical concept, has been utilized to develop some functional materials by the present author and his coworkers. Fractal surfaces show super water- and even oil-repellent property due to their very large surface area. In order to realize the super water-repellent fractal surfaces some waxes (alkylketene dimer and triglycerides) were employed. These waxes interestingly form the fractal surfaces spontaneously. The formation mechanism of the fractal structures on the wax surfaces has been made clear. The waxes which form the fractal surfaces have a meta-stable crystalline phase when solidified from their melts, and then transform to the thermodynamically stable crystal. During this phase transition process, the wax surfaces become fractal. For practical applications in future, durable super water-repellent and highly oil-repellent fractal surfaces have been synthesized by the electrochemical polymerization of an alkylpyrrole and the coating them with a fluorinated alkylsilane-coupling agents. In the final part of this article, the creation of a fractal body, not the surfaces, with a novel template method is mentioned. Such a fractal body is expected to show some interesting and unique functional properties.