Abstract
AbstractA common strategy to optimize whiteness in living organisms consists in using 3D random networks with dense and polydisperse scattering elements constituted by relatively low refractive index materials. Inspired by these natural architectures, a fast and scalable method to produce highly scattering porous polymer films via phase separation is developed. By varying the molecular weight of the polymer, the morphology of the porous films is modified, and therefore their scattering properties are tuned. The achieved transport mean free paths are in the micrometer range, improving the scattering strength of analogous low refractive index systems, e.g., standard white paper, by an order of magnitude. The produced porous films show a broadband reflectivity of ≈75% while only 4 µm thick. In addition, the films are flexible and can be readily index‐matched with water (i.e., they become transparent when wet), allowing for various applications such as coatings with tunable transmittance and responsive paints.
Highlights
Inspired by these natural design principles, we fabricated highly scattering white networks solely constituted by polymethylColors in nature are often obtained by evolutionary-optimized complex nanoscale architectures.[1,2] This optimization is truly extraordinary if one considers the constraints that living organisms face in assembling these structures (i.e., the low refractive methacrylate (PMMA) (Figure 1b,d)
The porous white films were obtained from PMMA by phase separation in solution (Figure 2a), a scalable process which is well known in the field of membrane technology.[12]
The bioinspired films obtained in this work reflect more than 75% in just a few micrometers of thickness while retaining two valuable features of PMMA: flexibility and lightweight
Summary
Inspired by these natural design principles, we fabricated highly scattering white networks solely constituted by polymethyl. We demonstrated that the scattering strength of the network can be indexes of the starting materials, the need for mechanical stability as well as lightweight).[3] In the case of bright iridescent colorations, periodic architectures that are only few micrometers in thickness are capable of providing all these properties.[4] In enhanced by varying the molecular weight of PMMA to achieve transport mean free paths (lt) as low as 1 μm for an incident wavelength around 500 nm. Having such a short transport mean free path yields a reflectance of 75% for a 4 μm thick film. The copyright line of this paper was changed 20 March 2018 after initial publication
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