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

作者：Stephanie L. Burg, A. L. Washington, David M. Coles, Antonino Bianco, Daragh McLoughlin, Oleksandr O. Mykhaylyk, Julie Villanova, Andrew J. C. Dennison, Chris Hill, Pete Vukusic, Scott Doak, Simon J. Martin, Mark Hutchings, Steven R. Parnell, Cvetelin Vasilev, Nigel Clarke, Anthony J. Ryan, W. R. Furnass, Mike Croucher, Robert M. Dalgliesh, Sylvain Prévost, Rajeev Dattani, Andrew Parker, Richard Jones, J. Patrick A. Fairclough, Andrew J. Parnell · 发表于：Communications Chemistry · 年份：2019 · DOI：10.1038/s42004-019-0202-8 · 被引用次数：44 · 研究领域：Block Copolymer Self-Assembly、Material Dynamics and Properties、Liquid Crystal Research Advancements

Abstract 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 fractions 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.