Synthesis And Properties Study Of Polynorbornene Derivative Anion Exchange Membrane

Ionomer composing polymer as main structure and quaternary ammonium cations as functional groups called anion exchange membrane has been widely used in fuel cells and redox flow battery. Fuel cell application required anion exchange membrane as gas separator and hydroxyl conductor, also allowed the use of non-precious catalyst. When serve as separator for redox flow battery, cations among membrane structure can highly improve the coulombic efficiency by reduce the crossover of vanadium ions. While, low alkaline stability and low conductivity restricted the development of anion exchange membrane.In this paper, we designed the monomer 1,6-bi(N(methyl, norbornene-5,6-dimethylene))hexyl ammonium salt(HDHM-iodidie) and polymerized with norbornene as comonomer to give the poly(HDHM-norbornene-OH-) series anion exchange membrane. The membrane and monomer structure were characterized by 1H NMR, 13 C NMR and FTIR. Swelling ratio and water uptake are only 6.2 % and 28.04 % at 60 °C for membrane with 2.32 mmol·g-1 ion exchange capacity(IEC). The conductivity of Poly(HDHM-Norbornene- OH--12) and Poly(HDHM-Norbornene-Cl--12) AEMs at room temperature up to 27 mS·cm-1 and 14 mS·cm-1 separately, and increased with temperature quickly. TGA and mechanical strength test results showed that, Poly(HDHM-norbornene) series anion exchange membrane with high thermo and mechanical stability. After immersied into 2 M NaOH solution under room temperature, membrane showed good alkaline stability. while improve temperature to 60 °C, IEC only left 65 % after 384 h.The energy barrier of degradation pathways calculation reveled that the msot possible degradation mechanis m is Hofmann Elimination > Nucleophilic substitution. The highest power density of fuel cell with Poly(HDHM-Norbornene-OH--12) as electrolyte is 42.56 mW·cm-2, coulombic efficiency and energy efficiency of redox flow battery can reach 93 % and 77 %.