frank lee

Photonic cellulose aerogels with hierarchical structures are fabricated by combining self‐assembly and ice templating. The secondary macroporous structure changes under pressure, triggering a change in the optical properties of the aerogel from light scattering to chiral light reflection mode. This discovery enables the fabrication of mechanoresponsive aerogels that reversibly switch between white and bright structural colors.

Abstract

Pressure‐responsive chiral photonic aerogels are fabricated by combining liquid crystal self‐assembly and ice‐templating processes. The aerogels have a hierarchical structure in which the primary 2D chiral nematic structured walls of cellulose nanocrystals form ribbons that support a secondary 3D cellular network. Owing to the flexibility of the aerogels in solvent, the 3D structure of the aerogel can easily be transformed to a 2D structure by pressure‐induced rearrangement. The aerogels vary from white in color, which arises from light scattering, to a reflective photonic crystal displaying bright iridescent colors that depend on the immersed solvent. A solvent‐sensitive ink that shows quick color response to different solvents is designed using the pressure‐responsive photonic aerogel. This material demonstrates a new response mechanism for the design of smart and mechanoresponsive photonic materials.

The domino hexadehydro-Diels–Alder reaction transforms polyynes to benzynes to naphthynes to anthracynes to tetracynes (and beyond?)

The domino hexadehydro-Diels–Alder reaction transforms polyynes to benzynes to naphthynes to anthracynes to tetracynes (and beyond?), Published online: 20 July 2018; doi:10.1038/s41557-018-0075-y

Properly designed polyyne substrates are shown to undergo efficient cascades of thermal cycloaddition reactions initiated by (rate-limiting) benzyne formation. Proceeding through naphthyne, anthracyne or tetracyne intermediates, rapid access to highly fused, polycyclic aromatic compounds can be achieved.