Surface texturing of natural ‘urushi’ thermosetting polymer thin films

Abstract

Japanese lacquer, known as urushi, is a traditional natural resin used for numerous applications, including tableware, art and furniture. The main component of urushi is urushiol, which is a catechol derivative with a long unsaturated hydrocarbon side chain. Utilizing the characteristics of urushiol as a thermoset, we have demonstrated the surface texturing of an urushi thin film with a thermal imprinting technique. Thermal imprinting was conducted at 100 °C for 10 min by pressing a patterned mold onto the film, and an indented surface that replicated the surface of the mold was obtained. The static water contact angle was changed from 70±0.5° to 112±3° after the fabrication of pillared patterns on the surface. Moreover, the imprinted line and space patterns caused strong anisotropic wetting depending on the direction. Our results demonstrate that the texturing of urushi thin films is a useful technique for controlling the wettability of natural thermoset urushi thin films. Surface texturing of catechol derivative urushiol was achieved using a thermal imprinting technique. An indented surface was obtained by thermal curing at 100 °C for 10 min while pressing an urushi film with a patterned mold. The indented surface enhanced the static water contact angle in comparison with the flat urushi film.