Structural relationships for the design of responsive azobenzene-based lyotropic liquid crystals

Luke Giles, Joshua Marlow, Calum Butler, Geosmin Turpin, Liliana de Campo, Stephen Mudie, Charl F J Faul, Rico F. Tabor*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Light-responsive binary (azobenzene + solvent) lyotropic liquid crystals (LCs) were investigated by structural modification of simple azobenzene molecules. Three benzoic acid-containing azobenzene molecules 4-(4-(hydroxyphenyl)diazenyl)benzoic acid (AZO1), 3-(4-(hydroxyphenyl)diazenyl)benzoic acid (AZO2) and 5-(4-(hydroxyphenyl)diazenyl)isophthalic acid (AZO3) were produced with various amide substitutions to produce tectons with a variety of hydrophobicity, size and branching. The LC mesophases formed by binary (azobenzene + solvent) systems with low volatility solvents dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMF) as well as the protic ionic liquids ethylammonium formate (EAF) and propylammonium formate (PAF), were investigated using a combination of small-angle X-ray and neutron scattering (SAXS and SANS) as well as polarising light microscopy (PLM). Increasing alkyl group length was found to have a strong influence on LC phase spacing, and changes in the position of substitution on the benzene ring influenced the preferred curvature of phases. UV-induced trans to cis isomerization of the samples was shown to influence ordering and optical birefringence, indicating potential applications in optical devices.
Original languageEnglish
Pages (from-to)4086 – 4095
Number of pages10
JournalPhysical Chemistry Chemical Physics
Volume22
Early online date30 Jan 2020
DOIs
Publication statusPublished - 21 Feb 2020

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