Study On Epoxy-functionalized Polynorbornene And Its Preparation For Hybrid Alkaline Anion Exchange Membranes

Alkaline anion exchange membrane is the key material affect the performance of direct methanol fuel cell(DMFC).However,the alkaline anion exchange membrane based on polymer has poor alkalinity stability and high methanol permeability,which seriously limits its development.Polynorbornene(PNB)has good thermodynamic properties,methanol resistance and high chemical stability,while PNB has poor processing performance.The AEMs with good alkalinity stability and low methanol permeability based on polynorbornene could be prepared by improved the processability of polynorbornene.In this paper,a series of epoxy-functionalized polynorbornene with different 5-norbornene-2-methylene allyl glycidyl ether(MGENB)radios were synthesized via addition-type polymerization or ROMP-type polymerization.Further,the formation of interpenetrating network structure was cross-linked by epoxy group and silane coupling with quaternary ammonium groups,the quaternary ammonium ionic was introduced to conducted the hydroxyl ionic.The corresponding hybrid anion exchange membrane based on addition-type polynorbornene or ROMP-type polynorbornene were prepared.The functions of characteristics of polymerization behavior,different MGENB radios in polynorbornene and different contents of siloxane coupling agent in hybrid membranes were investigated.The details were as follows:(1)The copolymer of aP(BN/MGENB)was synthesized by using({{C10H8(O)C [N(2,6-Me2C6H3)]CH3}Pd(CH3)(PPh3)})/tetrakis(pentafluorophenyl)borate catalytic system.The addition-type copolymerization of a P(BN/MGENB)was confirmed by 1H NMR and FT-IR.QaP(BN/MGENB-SiO2-x)hybrid anion exchange membrane was prepared by hydrolysis and crosslinking of epoxy group in aP(BN/MGENB)with GA and TSPCA under acidic conditions.The QaP(BN/MGENB-SiO2-x)with different TSPCA content was prepared.The addition polynorbornene had good solubility and all of the hybrid membranes had low methanol permeability(1.14-2.04×10-7 cm2 s-1),good thermodynamic properties,good ionic conductivity and ionic exchange capacity.The IEC of Qa P(BN/MGENB-SiO2-20)hybrid membrane reached 1.33×10-3 eq g-1,and had the highest ionic conductivity(9.7×10-3 S cm-1)at 80 oC.The open circuit voltage of methanol/air fuel cell test was 0.45 V,and the maximum power density was 45.6 mW cm-2 when the current density was 86.1 mA m-2.(2)The copolymer of r P(BN/MGENB)was synthesized by using Grubbs' 1st catalyst.The ROMP-type copolymerization of rP(BN/MGENB)was confirmed by 1H NMR and FT-IR.QrP(BN/MGENB-SiO2-x)hybrid anion exchange membrane was prepared by hydrolysis and crosslinking of epoxy group in r P(BN/MGENB)with GA and TSPCA under acidic conditions.The QrP(BN/MGENB-SiO2-x)with different TSPCA content was prepared.The ROMP polynorbornene had good processing performance,the hybrid membranes had good ionic conductivity and low methanol permeability.The QrP(BN/MGENB-SiO2-10)hybrid membrane had the highest IEC(1.63×10-3 eq g-1),and had the highest ionic conductivity(41×10-3 S cm-1)at 80 oC.The open circuit voltage of methanol/air fuel cell test was 0.95 V,and the maximum power density was 46.7 mW cm-2 when the current density was 96.7 mA m-2.The ROMP hybrid membranes had better processability,ionic conductivity and ion exchange capacity,as well as poor mechanical properties and alkali stability.