Ultra-short helix pitch and spiral ordering in cholesteric liquid crystal revealed by resonant soft X-ray scattering. Issue 1 (6th December 2021)

• Record Type: Journal Article
• Authors: Smekhova, Alevtina; Novotná, Vladimíra; Fekete, Ladislav; Abrudan, Radu; Fondell, Mattis; Hamplová, Věra; Ostrovskii, Boris I.
• Is Part Of: Soft matter. Volume 18:Issue 1(2021)
• Page Start: 89
• Page End: 96
• Publication Date: 2021-12-06
• Subjects: Soft condensed matter -- Periodicals; 530.413
• DOI: 10.1039/d1sm01543e
• Languages: English
• ISSNs: 1744-683X

Abstract

Abstract : An ultra-short helix pitch of 104 nm was revealed by anomalous soft X-ray scattering at the carbon K edge and AFM technique in a room temperature cholesteric liquid crystal with a lactate unit in a molecular chain. Abstract : The spontaneous formation of chiral structures offers a variety of liquid crystals (LC) phases that could be further tailored for practical applications. In our work, the characteristic features of spiral ordering in the cholesteric phase of EZL10/10 LC were evaluated. To disclose resonant reflections related to a nanoscale helix pitch, resonant soft X-ray scattering at the carbon K edge was employed. The angular positions of the observed element-specific scattering peaks reveal a half-pitch of the spiral ordering p /2 ≈ 52 nm indicating the full pitch of about 104 nm at room temperature. The broadening of the peaks points to a presence of coherently scattering finite-size domains formed by cholesteric spirals with lengths of about five pitches. No scattering peaks were detectable in the EZL10/10 isotropic phase at higher temperatures. The characteristic lengths extracted from the resonant soft X-ray scattering experiment agree well with the periodicity of the surface "fingerprint" pattern observed in the EZL10/10 cholesteric phase by means of atomic force microscopy. The stability of LC molecules under the incident beam was proven by X-ray absorption spectroscopy in transmission geometry.