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The understanding of the interaction between light and complex, random structures is the key for designing and tailoring the optical appearance and performance of many materials that surround us, ranging from everyday consumer products, such as those for personal care, paints, and paper, to light diffusers used in the LED-lamps and solar cells. Here, it is demonstrated that the light transport in membranes of pure cellulose nanofibrils (CNFs) can be controlled to achieve bright whiteness in structures only a few micrometers thick. This is in contrast to other materials, such as paper, which require hundreds of micrometers to achieve a comparable appearance. The diffusion of light in the CNF membranes is shown to become anomalous by tuning the porosity and morphological features. Considering also their strong mechanical properties and biocompatibility, such white coatings are proposed as a new application for cellulose nanofibrils.

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Here, various transparent and white cellulose-based materials produced so far are highlighted.

Photonic materials with angular independent structural color are highly desirable because they offer the broad viewing angles required for application as colorants in paints, cosmetics, textiles or displays. However, they are challenging to fabricate as they require isotropic nanoscale architectures with only short-range correlation. In this article, porous microparticles with such a structure are produced in a single, scalable step from an amphiphilic, low molecular weight bottlebrush block copolymer (290 kDa). This is achieved by exploiting a novel 'controlled micellization' self-assembly mechanism within an emulsified toluene-in-water droplet. By restricting water permeation through the droplet interface, the size of the pores can be precisely addressed, resulting in structurally colored pigments that can be tuned to reflect across the visible spectrum. Such 'photonic pigments' have several key advantages over their crystalline analogues, as they provide isotropic structural coloration that suppresses iridescence and improves color purity without the need for either refractive index matching or the inclusion of a broadband absorber.

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A new high-frequency and short-wavelength collective mode specific to binary liquid mixtures with large mass difference is observed in a computer simulation of Lio.8Pbo.2 and discussed within the framework of the Mori-Zwanzig formalism. The mode shows linear dispersion in a wave-number regime 0.1 A "* < ^ < 0.6 A~^ but its propagation velocity is higher than the ordinary sound velocity by more than a factor of 3. Its attenuation is only weakly q dependent in contrast to the damping of ordinary sound. In Lio.8Pbo.2 "fast sound" entails motion of the lighter atoms only.PACS numbers: 61.25.MvWe report the existence of an additional propagating collective mode in binary liquid mixtures, confined to high frequencies and large wave numbers well beyond the hydrodynamic regime. It can be observed in inelastic neutron-scattering experiments or in computer simulation studies of two-component systems with large atomic-mass difference. Some of these systems may respond to a high-frequency short-wavelength perturbation with a density wave, which is supported by the light particles alone, essentially, without the heavy particles participating in the collective motion. Since the dispersion law of this excitation mode is much steeper in the linear region than that of the Brillouin peak of ordinary sound, we call the new mode "fast sound." We have observed fast sound in a computer simulation study ^ of a liquid alloy system of 250 particles in a periodic cell modeling Lio.gPbo.i^ at temperature r=1085 K and total number density w =0.045 58 A ~l Results for the partial dynamic structure factorsSss '(q\(o)

Hydroxypropyl cellulose (HPC) is a biocompatible cellulose derivative capable of self‐assembling into a lyotropic chiral nematic phase in aqueous solution. This liquid crystalline phase reflects right‐handed circular polarized light of a specific color as a function of the HPC weight fraction. Here, it is demonstrated that, by introducing a crosslinking agent, it is possible to drastically alter the visual appearance of the HPC mesophase in terms of the reflected color, the scattering distribution, and the polarization response, resulting in an exceptional matte appearance in solid‐state films. By exploiting the interplay between order and disorder, a robust and simple methodology toward the preparation of polarization and angular independent color is developed, which constitutes an important step toward the development of real‐world photonic colorants.