Liquid – liquid phase separation morphologies in ultra-white beetle scales and a synthetic equivalent

Cyphochilus beetle scales are amongst the brightest structural whites in nature, being highly opacifying whilst extremely thin. However, the formation mechanism for the voided intra- scale structure is unknown. Here we report 3D x-ray nanotomography data for the voided chitin networks of intact white scales of Cyphochilus and Lepidiota stigma. Chitin-filling frac- tions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their density. Optical simulations using finite- difference time domain for the chitin morphologies and simulated Cahn-Hilliard spinodal structures show excellent agreement. Reflectance curves spanning filling fraction of 5-95% for simulated spinodal structures, pinpoint optimal whiteness for 25% chitin filling. We make a simulacrum from a polymer undergoing a strong solvent quench, resulting in highly reflective ( 94%) white films. In-situ X-ray scattering confirms the nanostructure is formed through spinodal decomposition phase separation. We conclude that the ultra-white beetle scale nanostructure is made via liquid–liquid phase separation

Correlating polyamide powder flowability to mechanical properties of parts fabricated by additive manufacturing

This study investigates the relationships between the flow properties of five blends of polyamide 12, with the mechanical and physical characteristics of the fabricated components. The bulk properties and flowability of the powder blends were characterised using powder rheology. Absolute, or skeletal volume of 3D printed cubes were measured using helium pycnometry. The tensile behaviour and surface hardness of specimens fabricated from the five blends were determined. The mechanical properties of the samples were correlated with the flow behaviour of the powder used. Comparison of the powder flow measures with the mechanical properties of the fabricated parts allows for prediction of final product quality prior to printing. Understanding the relationships between these parameters helps to identify and develop powders that enhance both process efficiency and the mechanical properties of the final product

Conformation and Interactions of Polystyrene and Fullerenes in Dilute to Semidilute Solutions

We report the polymer conformation and fullerene aggregation in a ternary system containing polystyrene, C₆₀, and toluene measured by small angle neutron, static, and dynamic light scattering. We investigate polymer concentrations across the dilute and semidilute regime for five polymer molecular weights (<i>M</i>_w = 20 kg/mol to 1 Mg/mol), and fullerene concentrations below and above its miscibility threshold in toluene. We find that the polymer radius of gyration (<i>R</i>_g^poly), hydrodynamic radius (<i>R</i>_h), and the mixture correlation length (ξ) remain unchanged upon addition of C₆₀. The miscibility of C₆₀ in toluene, however, decreases upon addition of polystyrene forming aggregates with a time-dependent radius on the order of 100 nm, and this effect is amplified with increasing polymer <i>M</i>_w. Our findings are relevant to the solution processing of organic photovoltaics, which generally require the effective solubilization of fullerene derivatives and polymer pairs in this concentration range

Crystallization of Nanocrystals in Spherical Confinement Probed by <i>in Situ</i> X‑ray Scattering

We studied the formation of supraparticles from nanocrystals confined in slowly evaporating oil droplets in an oil-in-water emulsion. The nanocrystals consist of an FeO core, a CoFe₂O₄ shell, and oleate capping ligands, with an overall diameter of 12.5 nm. We performed <i>in situ</i> small- and wide-angle X-ray scattering experiments during the entire period of solvent evaporation and colloidal crystallization. We observed a slow increase in the volume fraction of nanocrystals inside the oil droplets up to 20%, at which a sudden crystallization occurs. Our computer simulations show that crystallization at such a low volume fraction is only possible if attractive interactions between colloidal nanocrystals are taken into account in the model as well. The spherical supraparticles have a diameter of about 700 nm and consist of a few crystalline face-centered cubic domains. Nanocrystal supraparticles bear importance for magnetic and optoelectronic applications, such as color tunable biolabels, color tunable phosphors in LEDs, and miniaturized lasers

Crystallization of Nanocrystals in Spherical Confinement Probed by <i>in Situ</i> X‑ray Scattering

We studied the formation of supraparticles from nanocrystals confined in slowly evaporating oil droplets in an oil-in-water emulsion. The nanocrystals consist of an FeO core, a CoFe₂O₄ shell, and oleate capping ligands, with an overall diameter of 12.5 nm. We performed <i>in situ</i> small- and wide-angle X-ray scattering experiments during the entire period of solvent evaporation and colloidal crystallization. We observed a slow increase in the volume fraction of nanocrystals inside the oil droplets up to 20%, at which a sudden crystallization occurs. Our computer simulations show that crystallization at such a low volume fraction is only possible if attractive interactions between colloidal nanocrystals are taken into account in the model as well. The spherical supraparticles have a diameter of about 700 nm and consist of a few crystalline face-centered cubic domains. Nanocrystal supraparticles bear importance for magnetic and optoelectronic applications, such as color tunable biolabels, color tunable phosphors in LEDs, and miniaturized lasers

Crystallization of Nanocrystals in Spherical Confinement Probed by <i>in Situ</i> X‑ray Scattering

We studied the formation of supraparticles from nanocrystals confined in slowly evaporating oil droplets in an oil-in-water emulsion. The nanocrystals consist of an FeO core, a CoFe₂O₄ shell, and oleate capping ligands, with an overall diameter of 12.5 nm. We performed <i>in situ</i> small- and wide-angle X-ray scattering experiments during the entire period of solvent evaporation and colloidal crystallization. We observed a slow increase in the volume fraction of nanocrystals inside the oil droplets up to 20%, at which a sudden crystallization occurs. Our computer simulations show that crystallization at such a low volume fraction is only possible if attractive interactions between colloidal nanocrystals are taken into account in the model as well. The spherical supraparticles have a diameter of about 700 nm and consist of a few crystalline face-centered cubic domains. Nanocrystal supraparticles bear importance for magnetic and optoelectronic applications, such as color tunable biolabels, color tunable phosphors in LEDs, and miniaturized lasers