Effect of alkoxy chain density on the mesogenic properties of aroylhydrazone based liquid crystals: synthesis, characterisation, photophysical and gelation behaviour

ABSTRACT

Three series of ester linkage containing aroylhydrazone based compounds have been synthesised where density and length of alkoxy chains are varied sequentially at ester end, keeping amide end of the molecule the same to investigate the effect of alkoxy chain density. The series of the compounds with single alkoxy chain at 4- position at ester terminal show nematic mesophase. The series with two alkoxy chains at 3- and 5- positions exhibit columnar rectangular mesophase and the series with three alkoxy chains at 3-, 4- and 5- positions show columnar oblique mesophase. It was observed that increasing the number of alkoxy chains at ester terminal, self-assembly of molecules changes and leads to a change from nematic to columnar mesophase and also significant enhancement in the mesomorphic range. Temperature dependent Raman studies confirm the presence of intermolecular hydrogen bonding which assist the self-assembly and gelation properties of molecules. All the series show similar photophysical properties despite the fact that the series vary in their molecular structures. Representative compounds of each series exhibited gelation in hydrocarbon solvents. FESEM images of the gels showed interwoven network of nanofibers of several micrometres length. These supergelators may be good candidates for applications in electronic devices.

Graphical Abstract

KEYWORDS:

• Self-assembly
• nematic
• columnar rectangular/oblique mesophase
• ester linkage
• hydrogen bonding

Acknowledgments

We thank Interdisciplinary School of Life Sciences (ISLS), BHU for mass spectral analysis. We are thankful to Prof. B. Ray, Department of Chemistry, BHU for fluorescence studies. Central Instrumentation Facility of IIT BHU is acknowledged for FESEM studies. We thank Prof. Ranjan Kumar Singh, Department of Physics, BHU for temperature dependent Raman studies.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by DST, New Delhi [Grant No. SR/S1/IC-08/2012]; DST-PURSE [5050 scheme]; DST, SERB [N-PDF (PDF/2016/001706)]; DST Nano-Mission [SR/NM/NS-1212/2013] and UGC, New Delhi [BSR Faculty Fellowship].