Extending Polymer Opal Structural Color Properties into the Near-Infrared

• Published in: Micro Vol. 4; no. 2; pp. 387 - 400
• Main Authors: Giselle Rosetta, Matthew Gunn, John J. Tomes, Mike Butters, Chris E. Finlayson
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.06.2024
• Subjects: micro-particles; near-infrared spectroscopy; photonic crystals; polymer composites; thin-film coatings
• ISSN: 2673-8023
• DOI: 10.3390/micro4020024

We report the fabrication and characterisation of near-IR reflecting films and coatings based on shear-assembled crystalline ensembles of polymer composite microspheres, also known as “polymer opals”. Extension of the emulsion polymerisation techniques for synthesis of tractable larger core-interlayer-shell (CIS) particles, of up to half a micron diameter, facilitates the engineering and processing of thin-film synthetic opals, with a tunable photonic stopband spanning an extended spectral range of λ ≈ 700–1600 nm. Samples exhibit strong “scattering cone” interactions, with considerable angular dependence and angle tuning possible, as measured with a goniometric technique. These intense optical resonances in the near-IR, particularly within the important region around λ ~ 800 nm, combined with an appreciable translucency within the visible light spectrum, is indicative of the potential applications in coatings technologies and solar cells.