Biomineral-Inspired Organic/Inorganic Colloidal Liquid-Crystalline Hybrids for Photoresponsive Adhesion

Bioinspired hybrid nanostructures offer a promising strategy for developing dynamic functional materials. Herein, we report a new class of photoresponsive liquid-crystalline (LC) adhesives based on organic/inorganic nanostructured colloidal hybrids. These LC materials are composed of a biomineral-inspired hydroxyapatite (HAp) nanorod and azobenzene-based forklike molecules. The organic/inorganic LC hybrids exhibit unusual photo-enhanced adhesion upon photoinduced order–disorder phase transitions of these LC materials. The photoresponsive adhesion functions of the colloidal LC hybrids are tuned by spacer moieties of the forklike molecules as well as mixing of the hybrids with the forklike molecules. The reversible photo-enhanced adhesion of the LC hybrids is achieved when the forklike molecule having oligooxyethylene spacers is hybridized with the HAp nanorod. The flexible oligooxyethylene spacers of the forklike molecule are effective for the formation of less ordered packing of the azobenzene units in the LC hybrids, which enables the dynamic photoresponsive functions. We propose an approach to the development of bioinspired photoresponsive LC materials through self-assembly of functional organic molecules and biomineral-based colloidal hybrids.