Preparation Of Anion Exchange Membranes For Electrodialysis And Fuel Cell

Alkaline fuel cells (AFCs) are one of the most promising clean energy technologies under development. On the other hand, Electrodialysis (ED) is used for the production of ultra-pure water, the highly proficient desalination of brackish water, water softening and the removal of other charged contaminations from water streams. However, those will require chemically stable ion exchange membranes (IEMs) to make sure long performance lifetimes.Our present research emphases on developing different polymer systems (semi-interpenetrating polymer, side-chain type densely functionalized, and/or cross-linked polymers) in order to realize membrane in many features and design improved AEMs with better ionic conductivity, mechanical integrity and alkaline stabilityA series of brominated poly-(2,6-dimethyl-phenylene oxide) (BPPO)-based cross-linked AEMs containing clustered of tetra-alkyl ammonium (TAA) groups at side chain were prepared by attaching a novel (tris[2-(dimethylamino)ethyl]amine on polymer backbone via Menshutkin reaction followed by methylation resulting a novel class of ionomers containing clusters of four quaternary amine groups per repeat unit at side chain. The membranes formed were robust and transparent. The results suggest that the tactic of clustering TAA groups at side-chain to produce AEM can mitigate water swelling, enhance hydroxide conductivity and improve the stability of quaternary ammonium groups in AEMs. Moreover, we have synthesized crosslinked membrane via a simple and facile way by immersing halogenated polymeric (BPPO) membrane into dimethyl amine solution at room temperature, with great efficiency. Thus the membranes formed were transparent and flexible. They have good mechanical properties and low water uptakes but good hydroxide ion conductivities. Furthermore, the alkaline stability of x-CT-PPO-y membranes showed nearly no change in hydroxide conductivity and indicated that these membranes are good candidates for use in alkaline fuel cells. Also, we have prepared semi-interpenetrating polymer network (semi-IPN) composite ion-exchange membranes by crosslinking polymerization of [2-(acryloyloxy) ethyl]trimethylammonium chloride, styrene and divinylbenzene in presence of binder polymer poly(vinylidene fluoride) (PVDF). Thus, the semi-IPN composite membranes were fabricated with no extra processing steps. The investigation showed that prepared composite porous ion-exchange membranes exhibited good electrochemical transport properties. The composites prepared with 45% acrylate particles showed excellent performance in the desalination of the NaCl solution by ED at 7 volts, which was perceptibly similar to the performance of the Neosepta membrane. This thesis has created the structure-property relationships and effective synthetic method which will provide route for the improvement of next generation (AEM) materials.