Photoisomerization behavior of bisbenzylideneacetone/cycloheptanone and 1,3,4-oxadiazole containing nematic liquid crystalline polyesters under UV irradiation was investigated. Solubility, carbonyl group absorption band in FTIR, optical microscopy observation, as well as DSC analysis through existence of liquid crystallinity after irradiation were proved this phenomenon. Fluorescence spectra revealed blue-emission maxima with Stokes shift in the range of 46-49 nm. Band gap energy calculated from absorption spectra are in the range of 3.18-3.41 eV. Structure-property relationships were probed by correlating the spacer length with development of mesophase formation, thermal, and optical properties. Optical property of polymers disclosed photoisomerization processes. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 1902-1912, 2010