Mesomorphic andtrans–cis–transphotoisomerization studies of 4-[2-(4-hexyloxyphenyl)diazenyl]phenyl alkanoates

In this paper a full new homologues series of 4-[2-(4-hexyloxyphenyl)diazenyl]phenyl alkanoates is presented. All 15 synthesized compounds are mesogenic. Using differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffraction (XRD) measurements four mesophases (nematic, smectic C, G and H) were identified. Moreover, with ultraviolet (UV) irradiation the photoisomerization was induced. Next the process of thermal relaxation in the dark was studied by using the UV–visible (UV–Vis) spectroscopy. The data gathered allowed us to calculate the kinetic constant of the photoisomerization. Additionally, the trans and cis isomers were separated by using column gel chromatography and their UV–Vis spectra were measured.