Preparation Of Grafted Amphiphilic Peek Anion Exchange Membrane For VRB Application Via RAFT Polymerization

Vanadium redox flow battery (VRB) has received considerable attention in recent years due to its attractive features such as it’s flexibility in design, long life and fast response. The ion exchange membrane is one of the key materials in VRB. In this thesis, novel amphiphilic grafted anion-exchange membranes (AEMs) for VRB were synthesized by reversible addition fragmentation transfer (RAFT) polymerization.Initiated by AIBN, the2-(dimethylamino)ethyi methacrylate (DMAEMA) and1-vinylimidazole (VI) were separately grafted onto three different types of PEEK macromolecular chain transfer agent (macro-CTA). The resulting grafted copolymers are PEEK-1Ss, PEEK-2Ss and PEEK-Us. These copolymers can be easily processed into anion exchange membrane by flow casting.The composition, structure and molecular weight of the grafted copolymers were characterized by1H-NMR, FT-IR and GPC. The hydrophilicity, stability, electrical conductivity of the membranes were investigated by contact angle measurement, ion exchange capacity and TG. The results show that PDMAEMA and PVI were successfully grafted onto PEEK.The proton conductivity and vanadium permeability of QAPEEK-1S、QAPEEK-2Ss and QAPEEK-1Js membranes were measured. The results are compared with that of the Nafion117membrane. It is revealed that the proton conductivity of all these membranes is only slightly lower than that of Nafion117membrane under the same conditions. On the other hand. the vanadium permeability of the prepared membranes is lower than that of Nafion117membrane. The coulombic efficiency (CE) of VRB with the synthesized QAPEEK-1Js membrane is higher than that of VRB with Nafion117membrane. The highest coulombic efficiency (CE) of VRB based on QAPEEK-1J7membrane is82.90%. According to the membrane life test, the efficient working life of QAPEEK-1J7membrane is nearly twice as much as that of Nafion117membrane. The VRB based on the synthesized membrane shows good chemical stability in the process of continious circulation (60times) of charge and discharge. The values of CE、VE and EE are almost kept in the same level. The results indicate that the synthesized membranes have great potential for the application in VRB.