In this research, ionomeric composites based on organophilized silica (SIL) and a thermoplastic elastomer (HSBR), were prepared and characterized from a microstructural and electrical point of view. DSC was used to confirm silica sulfonation and FTIR to characterize the polymer before and after sulfonation reaction. DSC and DMA analysis show that T-g(HPB) remains constant in all the samples studied. T-g(PS) measured through DMA presents an increase of about 40degreesC in the sample containing both the sulfonated filler and the sulfonated polymer matrix. The resulting materials can be easily processed to yield thin films (thickness 0.2-0.4 mm) with outstanding proton conducting properties (10(-2) S (.) cm(-1)). The suitability for film formation and good electrical properties is indicative of their potential use as electrolytes in polymer fuel cells. (C) 2003 Wiley Periodicals, Inc.