In this work the synthesis of a semi aliphatic BTDA-DAH polyimide and their blends with BTDA-ODA and BTDA-DDS polyimides was carried out in order to improve the H(2) permselective properties of polyimides. The syntheses were made using the well-known two steps method and the silylation method. The prepared films were characterized by FTIR, DSC, thermal stability and fluorescence spectroscopy. Intercatenary distances (d-spacing) and gas separation properties were also investigated. PI blend membranes presented only one glass transition temperature (Tg) intermediate between those of the neat polyimides. Fluorescence spectra were a useful tool to recognize electron-donor and electron-acceptor interactions indicating intermolecular charge-transfer complex (CTC) formation which were confirmed by UV-Vis absorptions. As a result, a decrease in the intercatenary distances and a shift for both IR and fluorescence bands of polyimide blends were measured. PI blend membranes showed a permeability decrease with respect to the neat ones, while the selectivity increased according to X-ray diffraction results. To analyze the polyimide blend permselectivities, H(2)/CH(4), H(2)/CO(2), H(2)/O(2) and H(2)/N(2) systems were chosen. As a result, H(2)/CH(4) separation factor of PI blends was among the highest reported by other authors using traditional membrane materials. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.