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Structural color originates from the interference of light with periodic structures that feature characteristic length scales on the order of the wavelength of visible light. Long‐range order in photonic structures usually causes iridescence, and increasing disorder renders colors angle‐independent. Random disorder distributes scattering intensity over all wavelengths, producing white in the absence of absorption. Various non‐iridescent, vivid color patterns are found in Sternotomini longhorn beetles. Herein, Sternotomis virescens is investigated, where elytral scales produce a green‐blue color pattern on otherwise black elytra. Combining focused ion beam scanning electron microscopy (FIB‐SEM) tomography, ultra‐small‐angle X‐ray scattering (USAXS), structural modeling, and full‐wave optical simulations, it is found that the color originates from amorphous photonic networks based on sub‐units resembling the I‐WP unit cell, a triply‐periodic minimal surface with body‐centered‐cubic symmetry. This work provides insights into how quasi‐order produces stable colors in S. virescens longhorn beetles, highlights the advantages of volumetric imaging using FIB‐SEM tomography of porous nanostructured materials, and raises interesting questions about the formation mechanisms of amorphous structures in vivo. [ABSTRACT FROM AUTHOR]

Many commodity plastics, such as thermoplastic polyurethanes (PUs), require reinforcement for use as commercial products. Cellulose nanocrystals (CNCs) offer a "green" and scalable approach to polymer reinforcement as they are exceptionally stiff, recyclable, and abundant. Unfortunately, achieving efficient CNC reinforcement of PUs with industrial melt processing techniques is difficult, mostly due to the incompatibility of the hydrophobic PU with hydrophilic CNCs, limiting their dispersion. Here, a hydrophilic PU is synthesized to achieve strong reinforcement in melt‐processed nanocomposite fibers using filter paper‐sourced CNCs. The melt‐spun fibers, exhibiting smooth surfaces even at high CNC loading (up to 25 wt%) indicating good CNC dispersion, are bench‐marked against solvent‐cast films—solvent processing is not scalable but disperses CNCs well and produces strong CNC reinforcement. Mechanical analysis shows the CNC addition stiffens both nanocomposite films and fibers. The stress and strain at break, however, are not significantly affected in films, whereas adding CNCs to fibers increases the stress‐at‐break while reducing the strain‐at‐break. Compared to earlier studies employing a hydrophobic (and stiffer) PU, CNC addition to a hydrophilic PU substantially increases the fiber stiffness and strength. This work therefore suggests that rendering thermoplastics more hydrophilic might pave the way for "greener" polymer composite products using CNCs. [ABSTRACT FROM AUTHOR]

Approaches that enable the preparation of robust polymeric photonic particles are of interest for the development of nonfading and highly reflective pigments for applications such as paints and display technologies. Here, the preparation of photonic particles that display structural color in both, aqueous suspension and the dry solid state is reported. This is achieved by exploiting the confined self‐assembly of a supramolecular comb‐like block copolymer (BCP) that microphase separates into a well‐ordered lamellar morphology with dimensions that promote a photonic bandgap in the visible range. The comb‐like BCP is formed by robust ionic interactions between poly(styrene‐b‐4‐vinyl‐pyridine) (PS‐b‐P4VP) BCP and dodecylbenzene sulfonic acid (DBSA), which selectively interacts with P4VP blocks. The components are combined in chloroform, and an aqueous emulsion is prepared. Evaporation of the organic solvent leads to the formation of solid microparticles with an onion‐like 3D morphology. These photonic pigments display brilliant colors with reflectance spectra featuring pronounced optical bandgaps across the entire visible wavelength range with a peak reflectivity of 80–90%. [ABSTRACT FROM AUTHOR]