Modification Of Anion Exchange Membranes Based On Poly(2,6-dimethyl-1,4-phenylene Oxide)

Anion exchange membranes play an important role in alkaline anion exchange membrane fuel cells,which provide hydroxyl ions for ion conduction from cathode to anode during electrochemical reactions and separate the fuel from oxidants in the fuel cell.To meet the requirements of fuel cells,anion exchange membranes need to have high ionic conductivity and maintain high stability as well,ensure a good contaction with the electrodes for membrane electrode assembly.Therefore,preparation of anion exchange membranes possessing high-performance has been an important aim of this research field.In this thesis,anion exchange membranes of imidazolium functionalized poly(phenyl ether)were modified with different interpenetrating networks in order to enhance the mechanical properties of the membrane.Hydrophobic materials including polystyrene and poly(vinyl benzyl chloride)were used to fabricate the structure of the interpenetrating networks.Comprehensive characterization and comparisons of these membranes were made.The interpenetrating network could enhance the chemical stability and mechanical strength.The conductivity of the full-interpenetrating network membrane was 4.44 mS cm-1 at 60 ℃after immersing the membrane in 3 M KOH solution at room temperature for 120 h,which was higher than that(3.09 mS cm-1)of the membrane without the full-interpenetrating networks.The tensile stress at break of the membrane with full-interpenetrating networks was 8.2 MPa,which is comparible to that of the pristine anion exchange membrane based on imidazolium salt;while a higher elongation at break of 14%than that of 9.1%was achieved indicating the improved flexibility of the modified membrane.In order to improve the conductivity of the membrane,various contents of positively charged polystyrene particles were blended into the anion exchange membrane with full interpenetrating network.Along with the increase in the content of positively charged polystyrene particles,the ionic conductivity was increased as well.For the anion exchange membrane containing positively charged polystyrene particles of 10%,a high conductivity of 19.1 mS cm-1 was reached at 80 ℃,which was raised 54.0%comparing to the one without positively charged polystyrene at the same conditions.In addition,the retained conductivity at 60 ℃ was 7.15 mS cm-1 after immersing the membrane in 3 M KOH solution at room temperature for 120 h.