Resonant soft X-ray scattering studies of helical liquid crystals

Chenhui Zhu (Lawrence Berkeley National Laboratory)

Liquid crystals (LCs) form many interesting nano-scale structures, many of which can be probed with X-ray scattering techniques, typically hard X-rays due to its high penetrating power. However, in the hard X-ray regime, the scattering contrast of some LC nanostructures can be extremely low due to their weak electron density modulation. Here we show it is possible to use resonant soft x-rays to probe the helical pitch of the bent-core B4 helical nanofilament [1], which are essentially twisted smectic layers, and the newly discovered twist bend nematic phase [2], which is a new, more general phase between the uniaxial nematic and cholesteric phase. The in-situ temperature dependent measurements provide unique info on the materials properties, i.e. structure, pitch, elasticity, etc. This work shows the great potential of soft x-ray scattering in liquid crystals, and beyond.

[1] C. Zhu, C. Wang, A. Young, F. Liu, I. Gunkel, D. Chen, D. Walba, J. Maclennan, N. Clark, A. Hexemer, Nano Lett. 2015
[2] C. Zhu, M. Tuchband, A. Young, M. Shuai, A. Scarbrough, D. Walba, J. Maclennan, C. Wang, A. Hexemer, N. Clark, Phys. Rev. Lett. 2016

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