Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Focus: Smart Hydrogels and Hydrogel Based Devices I - organized by Gerald Gerlach, Walter Richtering and Thomas Hellweg

CPP 21.2: Vortrag

Dienstag, 13. März 2018, 10:00–10:15, C 130

Soft photonic crystals from core-shell mircogels — Astrid Rauh¹ and •Matthias Karg² — ¹Physical Chemistry I, University of Bayreuth, Universitaetsstr. 30, 95447 Bayreuth — ²Physical Chemistry I, Heinrich-Heine-University Duesseldorf, Universitaetsstr. 1, 40204 Duesseldorf

Photonic crystals are well known for their fascinating angle-dependent opalescence. In contrast to hard sphere building blocks, crystals from soft spheres such as microgels allow for external actuation, e.g. melting and recrystallization induced by pH or temperature changes. In addition, soft spheres can be deformed and thus packing fractions well above the hard sphere limit are accessible. A drawback with respect to the optical diffraction of soft photonic crystals is the typically low refractive index modulation inside the material. This asks for pathways to increase the refractive index contrast in the periodic superstructure.

We prepared cm-sized soft photonic crystals from core-shell microgels with absorbing nanocrystal cores (Au nanoparticles) and systematically studied the crystal structure and diffractive properties. As non-absorbing references, we prepared pitted particles from the same microgel batches by dissolution of the nanocrystal cores. The resulting purely organic microgels allowed for a direct comparison of structural and optical properties. We identify the role of small absorbing nanocrystal cores and show options to alter the photonic behavior of soft photonic crystals in future studies.

[1] A. Rauh et al., Langmuir 2017, DOI: 10.1021/acs.langmuir.7b01595