Linear sulfonated polyimides (SPFs) incorporating a difunctional PUSS unit, namely Phenylsbisaniline-PUSS, in the backbone of the main chain at concentration levels of 3, 5 and 10 mol% yield proton exchange membranes. Compared with other PUSS hybrid membranes fabricated by direct blending or cross-linking methods, the ultrafine PUSS aggregates show more uniform distribution and the obtained SPI-POSS co-polymers exhibit dramatically enhanced comprehensive properties as proton exchange membranes. The results reveal that the PUSS in the SPI main chain facilitates the dispersion of PUSS as a nano-filler and increases the confined bound water molecules within the formation of continuous proton transformation channels, thereby increasing the proton conductivity in comparison with the plain SPI without POSS. For example, the POSS-SPI membranes with Sand 10 mol% PUSS show higher conductivity in comparison to the PUSS free SPI (0.114 and 0.132 S cm(-1) vs. 0.0998 S cm(-1)) at 80 degrees C. Moreover, the obtained PUSS-SPI membranes also process enhanced oxidative and hydrolytic stabilities, low swelling ratio combined with high water uptake, adequate thermal stability and mechanical properties, as well as low methanol permeability. (C) 2015 Elsevier B.V. All rights reserved.