Sulfonated poly (phthalazinone ether ketone) and modified silica nanoparticles by poly (2-acrylamido-2-methyl-1-propanesulfonic acid) were prepared and their impact investigated on the physicochemical and transport properties of sulfonated poly ether sulfone. To optimize the weight percentage of incorporated components in sulfonated poly ether sulfone nanocomposite membranes and predict their performance, the central composite design (CCD) of the response surface method (RSM) was utilized. The independent parameters (weight percentage of added sulfonated poly (phthalazinone ether ketone) (SPPEK) and nanoparticles) and the responses (water uptake (WU), swelling ratio (SR), d value, proton conductivity, methanol permeability and selectivity) were developed and verified with experimental data. The optimum parameters for achieving the highest performance represented by proton conductivity of 57.9 mS cm(-1), methanol permeability of 3.21 x 10(-7) cm(2) s(-1), and membrane selectivity of 18.03 x 10(4) s S cm(-3) obtained at contents of SPPEK and nanoparticles of 23.07 and 3.9 wt%, respectively. The membrane with optimum additives demonstrated favorable direct methanol fuel cell (DMFC) characteristics such as reduced methanol permeability, high selectivity, and improved mechanical integrity as well as power density. (c) 2018 Elsevier Ltd. All rights reserved.