Alkoxy chain number effect on the mesomorphism, photophysical and gelation properties in aroylhydrazone-based mesogens

We report the synthesis, mesomorphic, photophysical and gelation behaviour of three series of aroylhydrazone-based polycatenars equipped with amide and ester linkages. All the series had two alkoxy chains at 3- and 5-positions at the amide end and the number and position of alkoxy chains at the ester end were sequentially increased. It was observed that the first series with alkoxy chain at 4-position at the ester end showed columnar oblique mesophase. Next, the series with alkoxy chain at 3- and 5-positions at the ester end showed columnar hexagonal mesophase. Further, the series with alkoxy chain at 3-, 4- and 5-positions at ester end showed columnar hexagonal mesophase. Similar absorption and emission spectra were observed for all the series. Only one compound showed gelation property with critical gelation concentration CGC (wt %) 1% or less than 1% in decane, dodecane and hexadecane. The FESEM image of the morphology of the gel showed a highly entangled network of nanofibers of several micrometres in length. Such mesogenic xerogels have immense potential for applications in optoelectronic devices.