As environmental issues such as global warming are deepening in the international society, researches on renewable energy are taking place to replace thermal energy sources. Among the new and renewable energies, researches on fuel cells are actively being carried out. Fuel cells are one-stage power generation systems and have the highest efficiency among currently available power generation technologies. In order to commercialize fuel cells, many problems have to be solved. Among them, it is essential to develop membranes to replace Nafion®.
In this study, poly(arylene ether)sulfone membrane was synthesized using an aromatic hydrocarbon system and the properties of the polymer electrolyte membrane were proceeded by comparing the position of the hydroxyl group in dihydroxynaphthalene.
Prior to the synthesis, 3D structure was drawn to predict the structure of the polymer, and there was a large difference in the hydrophobic part containing dihydroxynaphthalene. The physical properties and performance were compared using analytical methods such as 1H?NMR, FT?IR, GPC, TGA, DSC, and AFM.
It was confirmed that the polymer was synthesized well through the structural analysis using 1H?NMR and FT?IR. In the thermogravimetric analysis, the decomposition of the sulfonic acid group starts at about 240℃, and the glass transition temperature obtained through the differential scanning calorimetry is 180℃ and thus it is considered to be thermally stable. Moisture content and IEC were found to be higher by the effect of sulfonic acid groups on the block copolymer. The ionic conductivities were 52.6 mS/cm for BC 26-X35Y29, 7.4 mS/cm for BC 26-X84Y29 and 13 mS/cm for BC 27-X''35Y29 at 90℃.
BC 27-X''35Y29 showed lower IEC and ionic conductivity than BC 26-X35Y29 despite similar sulfonation degree. This was shown in the AFM phase image. In BC 26-X35Y29, a well- formed ion channel was observed which gave it the highest ionic conductivity. On the other hand, BC 27-X''35Y29, with similar degree of sulfonation, showed a lower IEC and ionic conductivity due to the blockage of the ion channel because of the aggregation of hydrophobic regions as predicted by the 3D structure drawn. In order to increase the ionic conductivity, it is necessary to effectively form an ion channel and synthesis of a block copolymer is very important in controlling that ion channel.