Abstract In nature, many animals protect themselves through deformation, discoloration, and infrared concealment to achieve multiple forms of camouflage. Camouflage fabrics designed for deserts and rainforests have vastly different requirements for color, breathability, and infrared emission. However, the development of corresponding smart fabrics remains a significant challenge. In this work, a novel dynamicâbondâcontrolled hygroâresponsive hydrochromic wool fiber artificial muscle, inspired by the octopuses, has been developed, which used to construct a smart multiâcamouflage fabric that integrates deformation, allochromasia, and infrared concealment. The obtained fabric exhibits a green color in humid environments (rainforests), with large pores for perspiration. In a dry environment (deserts), the fabric contracts and changes to akhaki color, while the reduction in pore size enhances infrared shielding. As the relative humidity increases from 20% to 100%, the average pore size of multiâcamouflage smart fabric decreases by âŒ84%, minimizing the radiative temperature difference between 36 °C target. This results in a temperature reduction of 5.2 °C for the target. The hydrochromic artificial muscle is also employed to develop smart fabrics that mimic octopusâlike behaviors. With its biocompatible, biodegradable, high thermal insulation, and comfortable wearability, the dynamicâbondâbased multifunctional muscle fabric opens up additional possibilities for smart textiles, information technology, and artificial intelligence.
Abstract The first example of luminescent monosubstituted polyacetylenes (monoâPAs) is presented, based on a contracted cisâcisoid polyene backbone. It has an excellent circularly polarized luminescence (CPL) performance with a high dissymmetric factor (up to the order of 10 â1 ). The luminescence stems from the helical cisâcisoid PA backbone, which is tightly fixed by the strong intramolecular hydrogen bonds, thereby reversing the energy order of excited states and enabling an emissive energy dissipation. CPL switches are facilely achieved by the solvent and temperature through reversible conformational transition. By taking advantages of fast response and high sensitivity, the thin film of monoâPAs could be used as a CPLâbased probe for quantitative detection of trifluoroacetic acid with a wider linear dynamic range than those of photoluminescence and circular dichroism. This work opens a new avenue to develop novel smart CPL materials through modulating conformational transition.
Elastic organic crystals have attracted considerable attention as next-generation flexible smart materials. However, the detailed information on both molecular packing change and macroscopic mechanical crystal deformations upon applied stress is still insufficient. Herein, we report that fluorescent single crystals of 9,10-dibromoanthracene are elastically bendable and stretchable, which allows a detailed investigation of the deformation behavior. We clearly observed a Poisson effect for the crystal, where the short axes (b and c-axes) of the crystal are contracted upon elongation along the long axis (a-axis). Moreover, we found that the Poisson's ratios along the b-axis and c-axis are largely different. Theoretical molecular simulation suggests that the tilting motion of the anthracene may be responsible for the large deformation along the c-axis. Spatially resolved photoluminescence (PL) measurement of the bent elastic crystals reveals that the PL spectra at the outer (elongated), central (neutral), and inner (contracted) sides are different from each other.