New Bulky Sulfonated Poly(ether sulfone) for Polymer Membrane Fuel Cells

Finding renewable alternative source of energy for non-renewable fossil fuels is one of the mostimportant issues of men in the past, now, and forever. Fuel cells which convert chemical energy toelectrical energy are regarded as promising future power sources [۱]. In recent years, research onproton exchange membrane fuel cells (PEMFCs) has increased significantly. Among several types offuel cells, polymer electrolyte membrane fuel cells are more studied and discussed [۲]. Nafion is themost popular and commercial membrane, widely used as the membrane in these types of fuel cells.However, these membranes have some disadvantages such as high cost, low conductivity at elevatedtemperatures, and high methanol crossover that advent searching for other materials with superiorproperties. In the past decade, a diversity of proton conductive materials, partially or completelyfluorinated polymers have been suggested as alternative membranes [۳]. Among them, sulfonatedpoly(arylene ether sulfone)s (SPAES)s exhibit remarkable properties in terms of chemical stability,thermal stability, mechanical strength, and low methanol permeability. Thus, the preparation andcharacterization of novel bulky sulfonated poly(ether sulfone)s were conducted in this research. For thispurpose, a new ۱,۴-dihydroxy anthraquinone-based bisphenol (BP) was prepared according to thereaction of ۱,۴-dihydroxy anthraquinone with ۴,۴’-dichlorodiphenyl sulfone (Scheme ۱). Then, a seriesof novel sulfonated poly(ether sulfone)s were prepared using direct copolymerization of ۳,۳′-disulfonated-۴,۴′-difluorodiphenyl sulfone as synthesized sulfonated dihalide and difluorodiphenylsulfone as nonsulfonated dihalide monomer with the new synthesized diol (BP). Copolymers weresynthesized by polycondensation in different degrees of sulfonation (۲۵-۴۵%). ۱H-NMR and FT-IRspectroscopy, dynamic mechanical thermal analysis, thermogravimetric analysis, and tensile test wereused for characterization of prepared membranes. The inherent viscosity of synthesized copolymerswas in the range of ۱.۰۲-۲.۱۳ dL/g.The microstructure and morphology of the prepared membranes were studied and as shown in Figure ۱microphase separation occurred in membranes. Due to large hydrophobic and hydrophilic segmentslength (bulky structure), suitable microphase separation observed.Also, copolymers showed acceptable properties as proton exchange membrane for fuel cells. Ionexchange capacity of membranes was in the range of ۰.۶۶-۱.۲۳ meq/g. Membranes showed protonconductivities increased by increasing in degree of sulfonation and reached to ۰.۰۷ S/cm . Preparedmembranes were thermally stable up to ۲۸۰ °C and water uptake of these samples were in the range of ۱۲-۲۵ wt.%.

کلیدواژه ها:

Poly(arylene ether sulfone) ، Fuel cell membrane ، Dihydroxy anthraquinone ، Bulky structure