Organic-inorganic hybrid membranes based on poly(vinylidene fluoride-co-hexa fluoropropylene) (PVdF-HFP)/sulfosuccinic acid were fabricated with different nanometer sizes of silica particles. Morphological images reveal the embedded ceramic filler over the membrane. Structural characterizations were made by FT-IR and XPS, ensure the inclusion of sulfosuccinic acid and silica into the PVdF-HFP polymer matrix. Sulfonic acid groups promote the IEC values and greater swelling behavior. Silica content in the hybrid membranes had a great effect on crystalline character as well as thermal properties of the membranes. Decrease in the filler size creates an effective route of polymer-filler interface and promotes the protonic conductivity of the membranes. The high conductivities in the range of 10(-2) to 10(-3) S cm(-1) were achieved through synergistic interactions between the organic and inorganic moieties of the hybrid membranes. Due to these splendid features, the prepared hybrid membranes can be a trademark in the field of fuel cells. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.