Study On SEBS Alkaline Polymer Cross-linked Membrane Modified Grafting With Quaternary Ammonium Cation

Anion exchange membrane(AEM)is a key material in AEMFC.Its role is to transport ions,insulate anode fuels and support bipolar catalysts.This also requires that the AEM should have the characteristics of low fuel permeation rate,fast ion transport rate,low swelling ratio,stable chemical properties,not easy degradation of backbone and cations,and good mechanical properties.Poly(styrene-b-(ethylene-co-butylene)-b-styrene)(SEBS)copolymer is a triblock polymer with soft-hard block alternating block in which itself is prone to microscopic separation structures.Besides,the SEBS is a full carbon chain backbone without ether bonds so that the alkali stability is better than the ether-containing polyaromatics polymer.In this paper,SEBS polymer of all-carbon chains is selected as membrane backbone.Using direct crosslinking and organic-organic covalent composite crosslinking strategies,AEMs with significantly improved comprehensive properties were prepared.As follows:1.Synthesis and characterization of long-side double-cation type SEBS-based cross-linked membranes.To improve the ion conductivity and dimensional stability of the SEBS-based AEM,a series of AEMs with different carbon chain lengths were prepared by chloromethylation,quaternary ammonium,cross-linking,alkalization and solution casting using a long side-chain and double cation cross-linking strategy with three block polymer SEBS as the backbone.70C16-SEBS-TMHDA membrane shows the better ion channel.At 80?,the OH' conductivity of can reach 72.13 mS/cm,and the low swelling ratio makes the cross-linked membrane exhibit strong dimensional stability.By introducing long functional side chains into polymer SEBS,the ionic conductivity and of the membrane was improved by constructing the hydrophilic microphase separation structure,and the crosslinking modification was carried out by introducing double cationic crosslinking agent.It can improve the mechanical properties and dimensional stability of alkaline membrane.Synthesis and characterization of SEBS-based piperidine AEM.2.Synthesis and characterization of long-range graft TMA cation SEBS anion exchange membrane?The first preparation of a 94.2%bromhexylated SEBS polymer(SEBS-C6-Br).Then,the TMA cation was grafted on PS side chain,in contrast to SEBS-TMA membrane.The results show that the SEBS-C6-TAM can reach 110.4 mS/cm OH' conductivity at 80?,which shows better ion conductivity and alkaline resistance than SEBS-TAM.And unexpectedly,bromohexylated SEBS is not gelated when the cyclic cations are grafted at multifunctional sites,and provide another effective way to SEBS polymer modification.3.Synthesis and preparation of m-PTP-c-SEBS-C6 covalent crosslinked membrane.On the basis of the SEBS-C6-Br polymer prepared in system 2,the composite membranes were prepared by organic-organic covalent crosslinking of m-triphenylpiperidine(m-PTP)polymer and SEBS-C6-Br polymer.The results show that the OH-conductivity of 0.68Qr-m-PTP-c-SEBS-C6 composite membrane can reach 91.8 mS/cm at 80? and the power density can reach 195 mW/cm2.This is attributed to the fact that the optimized microphase separation to the fact that the optimized microphase separation channel promotes the ion conductivity of anion exchange membrane and the high crosslinking degree inhibits the swelling of the membrane.