Ionic Liquid-Based Poly(Phthalazinone Aryl Ether)s As Proton Exchange Membrane(PEM) Under Anhydrous Conditions At High Temperature

This paper studied on sulfonated poly(phthalazinone aryl ether)s containing ionic liquids (IL) as the proton conducter under anhydrous high temperature conditions, for the application of high temperature proton exchange membrane fuel cell(PEMFC). Three types of ILs named [N222][CH3COO],[N222][HSO4] and EMIMES, were synthesized, respectively, and their chemical structures were characterized by FT-IR and1H-NMR. The composite membranes were prepared by solution casting method from these ILs and sulfonated poly(phthalazinone ether sulfone ketone)s (SPPESK). In order to avoid the leakage of IL in composite membranes, ternary system composite membranes were prepared by sol-gel or alkene monomers in situ polymerization in the presence of SPPESK and ILs. The proton conductivity, mechanical properties and ion dissolution of IL of composite membranes were investigated systematically.The proton condctivities of composite membranes were investigated systematically under anhydrous conditions at high temperature. It was shown that there may be a hydrogen bond between ILs and SPPESK by FT-IR. The proton conductivities of SPPESK/IL composite membranes increased with the increase of temperature, the degree of sulfonation and the ionic liquid contents. Comparing to pure membranes, proton conductivities of composite membranes increased a number magnitude. Dissolution of ILs in membrane occurred mainly in the first day, afterwards very little dissolution happened.The SPPESK/[N222][CH3COO] composite membranes were prepared.,under anhydrous conditions at above 100℃,proton conductivities of these membranes were over 1.5mS/cm, and the tensile strengths were in the range of 28.6 to 58.1 MPa. Conductivity up to 5.4 mS/cm was achieved for the composite membrane containing 20wt% [N222][CH3COO] in SPPESK with a sulfonation degree of 120% at 130℃, the tensile strength of SPPESK120-20 was 58.1MPa,and IL leak percentage was 1.75%, after dissolving,the proton conductivity change was small.The SPPESK/[N222] [HSO4] composite membranes were prepared,whose conductivities were over 2.5mS/cm under anhydrous conditions at above 100℃,the proton conductivity of SPPESK100-40 was achieved 6.68 mS/cm at 130℃, and 28.2 MPa of tensile strength and 106.7 MPa of tensile modulus for SPPESK100-40,too. However, after cross-linking by sol-gel of SiO2, the proton conductivity under anhydrous conditions and mechanical propery of SPPESK/[N222][HSO4]/SiO2 composite membranes were drcreased, the tensile modules all achieved 1Gpa.but IL dissolution was lower, reduced the leakage to be possible to reach 35.7%.The SPPESK/EMIMES composite membranes were prepared,and their conductivities were over 1.1mS/cm at above 100℃under anhydrous conditions, and ion conductivity of SPPESK100-30 achieved 3.86 mS/cm at 130℃; The composite membranes of SPPESK/EMIMES/polyacrylic acid were prepared by an in situ polymerization of acrylic acid/SPPESK/EMIMES, and the proton conductivity of was over 5.8 mS/cm for the composite membrane containing 20wt% EMIMES and 15wt% polyacrylic acid in SPPESK100 at 100℃, and achieved 6.36 mS/cm at 130℃,and dissolvent reduced to the composite membrane quality 1.72%. SPPESK100-EMIMES and SPPESK100-EMIMES-PPA composites had good mechanical properies as well, and the tensile strength fell into 26.8 to 39MPa, which is higher than the Nafion membrane.The ionic liquid-based sulfonated poly(phthalazinone aryl ether)s shown good proton conductivity under high temperature and anhydrous conditions,good mechanical propety and fine stability,making them a prosperous proton exchange membrane materials.