Browsing by Author "Tokumasu, Takashi"

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    Article
    Mesoscale Morphologies of Nafion-Based Blend Membranes by Dissipative Particle Dynamics
    (MDPIST ALBAN-ANLAGE 66, CH-4052 BASEL, SWITZERLAND, 2021) Sen, Unal; Ozdemir, Mehmet; Erkartal, Mustafa; Kaya, Alaattin Metin; Manda, Abdullah A.; Oveisi, Ali Reza; Ali Aboudzadeh, M.; Tokumasu, Takashi; 0000-0002-1940-8749; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Kaya, Alaattin Metin
    Polymer electrolyte membrane (PEM) composed of polymer or polymer blend is a vital element in PEM fuel cell that allows proton transport and serves as a barrier between fuel and oxygen. Understanding the microscopic phase behavior in polymer blends is very crucial to design alternative cost-effective proton-conducting materials. In this study, the mesoscale morphologies of Nafion/poly(1-vinyl-1,2,4-triazole) (Nafion-PVTri) and Nafion/poly(vinyl phosphonic acid) (Nafion-PVPA) blend membranes were studied by dissipative particle dynamics (DPD) simulation technique. Simulation results indicate that both blend membranes can form a phase-separated microstructure due to the different hydrophobic and hydrophilic character of different polymer chains and different segments in the same polymer chain. There is a strong, attractive interaction between the phosphonic acid and sulfonic acid groups and a very strong repulsive interaction between the fluorinated and phosphonic acid groups in the Nafion-PVPA blend membrane. By increasing the PVPA content in the blend membrane, the PVPA clusters' size gradually increases and forms a continuous phase. On the other hand, repulsive interaction between fluorinated and triazole units in the Nafion-PVTri blend is not very strong compared to the Nafion-PVPA blend, which results in different phase behavior in Nafion-PVTri blend membrane. This relatively lower repulsive interaction causes Nafion-PVTri blend membrane to have non-continuous phases regardless of the composition.
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    Proton-conducting blend membranes of Nafion/poly(vinylphosphonic acid) for proton exchange membrane fuel cells
    (SPRINGER, 2013) Acar, Oktay; Celik, Sevim Unugur; Bozkurt, Ayhan; Ata, Ali; Tokumasu, Takashi; Miyamoto, Akira; Sen, Unal; 0000-0003-4201-370X; 0000-0001-6055-2817; 0000-0003-3736-5049; AGÜ, Mühendislik Fakültesi, Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü; Sen, Unal
    Nafion/poly(vinylphosphonic acid) blends were synthesized and characterized in this work. Poly(vinylphosphonic acid), PVPA, was synthesized by the free-radical polymerization of vinylphosphonic acid. Then Nafion/PVPA blend membranes were prepared by means of film casting from Nafion/PVPA solutions with several molar ratios of PVPA repeat unit to – SO3H. Homogeneous Nafion/PVPA films were produced. Nafion–PVPA interactions were studied by Fourier transform infrared (FT-IR) spectroscopy. Thermal properties were investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TGA results illustrated that all of these Nafion/PVPA electrolytes are thermally stable up to 400 °C. The membrane properties were further characterized by studying their morphologies using scanning electron microscopy (SEM). The proton conductivity of the Nafion/P(VPA)3 blend membrane was 1.1×10−5 S/cm in an anhydrous state at 130 °C. The conductivities of the blends increased by at least three orders of magnitude upon hydration, exceeding 10−2 S/cm with RH=50 % at ambient temperature