Light-responsive bent-core liquid crystals as candidates for energy conversion and storage

Ivan Dominguez-Candela, Iman Zulkhairi, Inmaculada C. Pintre, Nurul Fadhilah Kamalul Aripin, Jaime Lora García, Vicent Fombuena Borrás, M. Blanca Ros, Alfonso Martinez-Felipe* (Corresponding Author)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

We have assessed the potential of light-responsive bent-core liquid crystals as candidate materials for energy conversion and storage applications. Samples comprise two chromophore bent-core compounds containing either one (IP33) or two (IP31) azobenzene groups, and their 5% (molar) mixtures with one non-chromophore bent-core compound (NG75), which was also measured as a reference material. The pristine compounds and their mixtures were introduced in thin transparent Indium Tin Oxide (ITO) cells, and were characterised by polarised optical microscopy, UV-visible spectrophotometry, impedance spectroscopy, and ferroelectric analysis, under different conditions of electrical fields and UV irradiation. All materials display smectic C polar phases (SmCP) except IP31, which forms columnar phases (Col), and IP33, IP31 and their mixtures exhibit light-responsiveness when irradiated at 365 nm due to reversible trans-to-cis photoisomerisation of the azobenzene units. All the bent-core based materials exhibit, at least, two dielectric relaxations, associated to different modes of molecular reorientation under weak alternating electrical fields (1 Vrms), as well as ferroelectric response that leads to permanent polarisation under the application of strong alternating fields (~ 75 kV·cm-1) at frequencies associated to the Goldstone-mode (1 Hz). Samples show considerable conductivity values and relaxor behaviour for liquid crystals, which can be tuned by application of UV light. In addition, we have induced in IP31 isothermal phase transitions from columnar to smectic phases (via the isotropic melt), by a combination of light and electrical stimuli. Our results confirm the potential of these bent-core compounds as light-harvesters for energy applications.
Original languageEnglish
JournalJournal of Materials Chemistry C
Early online date16 Nov 2022
DOIs
Publication statusE-pub ahead of print - 16 Nov 2022

Keywords

  • azobenzenes
  • bent-core liquid crystals
  • ferroelectricity
  • dielectric spectroscopy
  • energy storage

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