Photo-responsive graphene oxide liquid crystal hybrid modified with imidazolium surfactant containing azobenzene

A novel photo-responsive imidazolium surfactant containing azobenzene mesogenic cores (CAzoCM) was designed and synthesised to modify graphene oxide, forming imidazolium surfactant-graphene oxide hybrid (CAzoCM-GO), focusing on the correlation between their mesomorphic behaviour, photo-responsive properties and their chemical structure. CAzoCM and CAzoCM-GO were characterised by FT−IR, Raman spectroscopy and XPS, respectively. The results showed that GO was partially reduced by CAzoCM due to the strong electron effect of the imidazole group. The liquid crystal properties of CAzoCM and CAzoCM-GO were investigated by DSC, POM and variable temperature XRD, respectively. CAzoCM exhibited a smectic A phase as well as the rare smectic C phase and the introduction of GO did not destroy the liquid crystal properties of CAzoCM. Furthermore, the photo-responsive behaviour of CAzoCM and CAzoCM-GO had also been studied by UV-vis spectrum. CAzoCM could be switched from trans to cis isomer in 270 s when it was irradiated under ultraviolet light and from cis to trans isomer in 660 s when it was irradiated under visible light. CAzoCM-GO exhibited more sensitive response behaviour, the photo-responsive time from trans to cis isomerisation became 110 s while the photo-responsive time from cis to trans isomerisation became 195 s.