Heterogeneous sulfonation of blend systems based on hydrogenated poly(butadiene-styrene) block copolymer. Electrical and structural characterization

Conducting membranes of hydrogenated poly(butadiene-styrene) block copolymer (HPBS) were obtained by heterogeneous sulfonation and then their electrical properties were studied. In addition, the effects of PP content on the morphology of these blends, as well as their conducting properties, were considered. The degree of sulfonation was determined by means of photoelectron spectroscopy (XPS) and the structural characterization was carried out using differential scanning calorimetry (DSC) and dynamic-mechanical analysis (DMA). The results show that sulfonated HPBS has difficulties to be made into membranes besides reduced conductivity while the polymer blends with PP have high conductivity values and good dimensional stability. In this work, we find that increasing the PP content in the blend improves mechanical aspects, but on the other hand, conductivity decreases as the PP does not participate in the sulfonation process. The sample of composition 70% HPBS/30% PP sulfonated for 12 h with HClSO3 0.1 M (AMP-13S) was seen to be adequate as fuel cell membrane, especially due to the high conductivity properties and excellent dimensional stability. (C) 2001 Elsevier Science B.V. All rights reserved.