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Updated: Jan 7, 2026

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Synthesis, Mesophases, and Combined Thermal, Structural, and Spectroscopic Analysis of Photoresponsive Azobenzene
Marcin Piwowarczyk1, Aleksandra Deptuch1, Anna Drzewicz1
1Institute of Nuclear Physics Polish Academy of Sciences, Kraków PL-31342, Poland.
Abstract:
A homologous series of (E)-4-[(4-decyloxyphenyl)diazenyl]phenyl alkanoates (10OABOOCm, m = 1-19) was synthesized and investigated for thermal, structural, and photoresponsive properties. Phase behavior was studied by polarized optical microscopy, differential scanning calorimetry, and thermo-optical analysis. All derivatives exhibited liquid crystalline properties: nematic phase for short chains (m = 1-11), smectic A for two derivatives (m = 1 and 2), smectic C for most compounds (m = 2-19), additional hexatic smectic phases in narrower ranges (SmF: m = 6-13; SmI: m = 9-19), and crystal-like G phase (m = 2-9). X-ray diffraction and Fourier transform infrared spectroscopy confirmed layered packing and characteristic intermolecular interactions, while dielectric spectroscopy revealed relaxation processes in the crystalline phases. UV-vis absorption demonstrated efficient E-Z photoisomerization in solution, with a photostationary state reached within ∼100 s and a rate constant k = 2.81 × 10-2 s-1. These findings show that the terminal chain length influences mesophase formation, molecular organization, and photoresponsivity in this family of azobenzene-based liquid crystals.
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