Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene

We report the fabrication of hyperbranched hollow crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene on a concave surface of the spherical glass substrate by sublimation and their practical photomechanical behaviors. The number of units of the branched structure of the hollow crystals composed of this compound is proportional to the substrate curvature of the substrate. Compared with the sublimation process of the same compound on the flat glass substrate, two kinds of the thin film domains are generated separately in the center and around the edge of the spherical glass substrate. Especially under the high relative humidity condition, the boundaries between these thin film domains move gradually around the edge through the center during as long as 6 h of sublimation time so that the hyperbranched hollow crystals are densely produced on the entire surface of the substrate. These hyperbranched hollow crystals can be prepared with the highly ordered molecular packing due to the very slow formation process of the crystalline walls of the hollow structures. Furthermore, the photo-induced bending behaviors in the few- and highly-branched hollow crystals have the practical roles in moving and bending the minute objects according to their characteristics of these branched shapes. The sublimation process where the thin films of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene are formed on a concave surface of the spherical glass substrate, accompanying the movement of boundaries between the thin film domains under the higher relative humidity condition, leads to the fabrication of the hollow crystals having the highly branched shapes.image

Automated summary

In this study, hyperbranched hollow crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene were fabricated on a concave surface of a spherical glass substrate using sublimation. The number of branched structures in the hollow crystals was dependent on the substrate curvature. Compared to the sublimation process on a flat glass substrate, two distinct thin film domains were formed on the spherical glass substrate, and under high relative humidity conditions, the boundaries between these domains gradually moved from the center to the edge, resulting in the dense production of hyperbranched hollow crystals on the entire surface of the substrate.