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Tunable Diffraction Gratings in Copolymer Network Liquid Crystals Driven with Interdigitated Electrodes

2019; American Chemical Society; Volume: 1; Issue: 12 Linguagem: Inglês

10.1021/acsaelm.9b00579

2637-6113

Atefeh Habibpourmoghadam, Lukas Wolfram, Fatemeh Jahanbakhsh, Benedikt Mohr, Victor Reshetnyak, Alexander Lorenz,

Phase-change materials and chalcogenides

The diffraction behavior of a polymer network liquid crystal (PNLC) was studied in in-plane switching (IPS) test cells and compared to the behavior seen in a neat liquid crystal. Due to the presence of polymer, the diffraction behavior was varied drastically: PNLCs are composites, which possess a specific domain size. The size of such polymer-induced domains was investigated with polarized optical microscopy and scanning electron microscopy. PNLCs are capable of continuous optical-phase modulation. It was found that electrical addressing with nonhomogenous electric fields can be useful to vary the phase modulation profile as compared to a neat LC. The diffraction patterns seen in a nematic LC were influenced by the applied addressing voltage and showed some limited tunability already. However, in the PNLC, the diffraction patterns were drastically varied as compared to a neat nematic LC. These gratings showed responses localized to the electrodes, had higher tuneability, and could also be useful to partially suppress the zeroth-diffraction order. Depending on the applied voltage, the diffraction efficiency could be tuned, efficiently. The presented results are instructive to understand the impact of a polymer network on the field-dependent reorientation of the liquid crystal director: if addressed with the same electric field profile, the responses were much more localized than in a neat nematic LC. In a straightforward numerical approach, domains in the PNLC samples were described by using cuboids. Diffraction patterns were then calculated based on the director reorientations seen and compared to the experimental data.