The goal of this article was to synthesize a series of flexible polyimides containing ether linkage in main chain and clarified the effect of this ether linkage on some physical properties such as optical and thermal decomposition. Also, different functional group effects such as carbonyl (-C=O), hexa-fluoro-isopropylidene [-C(CF3)(2)-] and phenyl (-C6H5) on these physical properties were evaluated. The structural characterization of poly(ether imide)s was performed using Fourier transform infrared, H-1-nuclear magnetic resonance (NMR), and C-13-NMR techniques. Optical band gap of polyimides was calculated in the range from 2.57 to 2.81 eV. Thermal characterization of poly(ether imide)s was carried out using thermogravimetry-differential thermal analysis and differential scanning calorimetry. Thermal stability of poly(ether imide)s was evaluated by initial decomposition temperature (T-on) and char. T-on value of polymers was determined in the range from 100 to 195 degrees C. In addition, glass transition temperatures of poly(ether imide)s were found between 144 and 148 degrees C. (C) 2018 Wiley Periodicals, Inc.