Synthesis And Characterization Of Novel Triazole Proton Exchang Membrane

Perfluorinated vinyl sulfonic membrane such as Nafion, currently commercialized and bearing high proton conductivity, requires high relative humidity(RH), and low working temperature(about 80℃), which results in catalyst easyly to be poisoned and internal water and thermal management to be difficult. This research is from the International Collaboration Project of Henan Province, "Design and synthesis of novel heterocyclic proton exchange membrane”(No.104300510009), aiming to design and synthesize the novel non-fluorinated and high temperature resistant membrane. In this paper, novel proton exchange membrane based triazole functional group was prepared successfully by azide cycloaddition,condensation grafting, protection group removing and sol-gel processing. Structures of each intermediate were characterized by IR, 1H-NMR and 13C-NMR.First, benzyl azide(I) was prepared by azide reaction using benzyl chloride used as raw material. The optimized conditions were obtained by single factor experiments and orthogonal design: Solvent 15 mL, n(sodium azide): n(benzyl chloride)=1.25: 1, reacting 6h at 75℃, the yield of benzyl azide(I) is 83.89%.Secondly, 1-benzyl-4-hydroxymethyl--1H-1,2,3- triazole(II) was synthesized by click-cyclization using(I) and propargyl alcohol as raw materials. The optimized conditions were obtained by single factor experiments and orthogonal design: 25 mL mixed solvent of tetrahydrofuran and water, reacting 24 h at 63℃, the ratio of n(benzyl azide): n(propargyl alcohol): n(ascorbic acid): n(CuSO4?5H2O) = 1: 1.2: 0.2: 0.02. The yield of(II) reaches92.60%.Then, 1-benzyl-1,2,3-triazole-4-sodium methoxide was first prepared using(II) as the raw material. 1-Benzyl-4-{[3-(trimethoxysilyl) propoxy] methyl}-1,2,3- triazole(III) was successfully synthesized by Williamson grafting and condensation using g- chloropropyl trimethoxy silane(A) as precursor. The optimized process conditions were obtained through single factor experiment and orthogonal design: 20 mL methylene chloride as solvent, the mole ratio of(II), A and sodium = 1: 1: 1.5, reacting 12 h at temperature 40℃. The yield of(III) reaches 90.56%. And then, macromonomer 4-{[3-(trimethoxysilyl)] methyl}-1H-1,2,3-triazole(IV) was obtained by removing protecting group of benzyl. The yield of(IV) is 71.39% when trifluoroacetic acid is 15 mL and reacting at 80℃ for 42 h.At last, novel proton exchange membrane based triazole functional groups was prepared by sol-gel technique. Scanning electron microscopy reveals PTFE membrane micropores are filled with gum base material. TGA shows that the preparaed membrane has good thermal stability(260℃). The proton conductivity reaches 6.12×10-3 S·cm-1 at 160℃.