(307h) Responsive Nanocomposites Thorugh Hierarchical Assembly

Many fascinating biological systems like abalone shells and lotus leaves are only composed of ordinary materials. Their superior properties, however, arise from the meticulous control of structures and functionalities over multiple length scales. Drawing from nature, recent research has witnessed rapid advances in bio-inspired materials and has recognized self-assembly, the spontaneous organization of pre-programmed building blocks via noncovalent interactions, as the most promising approach. By deliberately controlling the assembly and programming the functionalities of building blocks, it is possible to construct hierarchically biomimetic systems with spatially defined structure and functionality.

The introduction of organic functional components into hierarchically porous inorganic scaffolds represents an important endeavor towards bio-inspired hybrid materials. Synthesis approaches involve either grafting organic moieties onto a preformed porous scaffolds or using functional organosilanes as building blocks. We report the first example of responsive mesoporous nanocomposites through cooperative assembly of silsesquioxanes containing a diacetylenic group. Subsequent topo-polymerization creates the responsive nanocomposites embedded with polydiacetylene (PDA), a polymer that chromatically responds (e.g., blue to red) to a wide range of external stimuli. Such a hierarchical molecular design endows the nanocomposites with thermochromatic reversibility, mechanical robustness, enhanced thermal stability, and rapid chemochromatic response. This research also provides an efficient molecular design and assembly paradigm to fabricate a family of conjugated optoelectronic materials, creating novel platforms for sensors, actuators, and other device applications.