Sevim Ünügür Çelik

Azole substituted polyphosphazenes as nonhumidified proton conducting membranes

Novel nonhumidified proton conducting membranes have been prepared from the reactions of triazole (Tri) and aminotriazole (Atri) compounds with poly[(4-methylphenoxy)chlorophosphazene] (PMPCP). The composition of the novel polymers (TriP and AtriP) was verified by elemental analysis (EA) and the structure was characterized by FT-IR, 1H and 31P NMR. Size exclusion chromatography was used to confirm the polymer formation. Thermogravimetric analysis (TGA) showed that the samples are thermally stable up to approximately 150 °C. Differential scanning calorimetry (DSC) results illustrated the homogeneity of the materials. To obtain sufficient proton conductivity at high temperatures in the anhydrous state, the polymers were doped with trifluoromethanesulfonic acid (TA) at various molar ratios, x = 0.5, 1, 2 and 3 with respect to the azole unit. The proton conductivity of the polymer electrolytes was measured using high resolution dielectric-impedance analyzer. The proton conductivity of these materials increased with dopant concentration and temperature. Maximum proton conductivity of TriP2TA and AtriP2TA were obtained as 3 × 10−3 S cm−1 at 50 °C and 0.0412 S cm−1 at 130 °C respectively, in the anhydrous state.

Enhancing the Anhydrous Proton Conductivity of Sulfonated Polysulfone/Polyvinyl Phosphonic Acid Composite Membranes With Hexagonal Boron Nitride

Hexagonal boron nitride (h-BN) particles have attracted increasing interest due to mechanical properties, chemical stability, electrical features, thermal stability, and good lubrication property. In this work hexagonal boron nitride were used as inorganic fillers, which increase the mechanical and thermal stabilities of the membrane. The proton conducting polymer membranes were prepared by blending of sulfonated polysulfone, polyvinyl phosphonic acid, and boron nitride. Scanning electron microscopy indicated the homogeneous distribution of hBN nanoparticles in the polymer matrix. hBN increased the proton conductivity and in the anhydrous state the maximum proton conductivity was determined as 7.9 × 10−3 S/cm at 150°C for PVPA-SPSU-5hBN. GRAPHICAL ABSTRACT

Fabrication and characterization of anhydrous polymer electrolyte membranes based on sulfonated poly(vinyl alcohol) and benzimidazole

In the present study, a new type of chemically cross-linked polymer blend membranes consisting of poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA) and benzimidazole (BnIm), as a dopant, at different stoichometric ratios were prepared and used as proton conducting polymer electrolytes. The proton conductivities of the membranes were investigated as a function of blending composition and the temperature. TGA indicated that the blend polymers were thermally stable up to approximately 175°C; differential scanning calorimetry (DSC) results illustrated the homogeneity of the materials. The local chain flexibility of the host polymer increased with BnIm concentration. The methanol permeability values of the membranes were much lower than that of a Nafion-membrane. The proton conductivity of these materials increased with BnIm and SSA concentration and the temperature.

Effect of hexagonal boron nitride on poly(vinyl phosphonic acid) composite polymer electrolytes for fuel cells

In this work, hexagonal boron nitride nanoparticles were used as inorganic fillers, which increase the mechanical and thermal stabilities as well as the proton conductivity of the proton conducting composite membranes prepared by blending of poly(vinyl phosphonic acid) and hexagonal boron nitride. Thermo gravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to 200°C. Scanning electron microscopy analysis indicated the homogeneous distribution of boron nitride nanoparticles in the polymer matrix. The crystallinity of the membranes was characterized by using X-ray Diffraction. X-ray patterns support semi-crystalline nature of the composite materials.

An investigation of proton conductivity of binary matrices sulfonated polysulfone/polyvinyltriazole after doping with inorganic acids

As anhydrous proton conductive membranes, sulfonated polysulfone (SPSU) and polyvinyl triazole were studied as binary matrices. The sulfonation of polysulfone was performed with trimethylsilylchlorosulfonate and high degree of sulfonation (140%) was obtained. Ion exchange capacity of SPSU was determined as 3.05 mmol−1/g. The polymer electrolyte membranes were prepared by blending of sulfonated polysulfone with polyvinyl triazole and phosphoric acid. Fourier transform infrared spectroscopy confirmed the sulfonation of the polysulfone and the ionic interaction between sulfonic acid and triazole units. Thermogravimetric analysis showed that the polymer electrolyte membranes are thermally stable up to at least 150°C. Scanning electron microscopy analysis indicated the homogeneity of the ternary composites. The maximum proton conductivity has been measured as 3.63 × 10−4 S cm−1 at 150°C.