Humidity effect on temperature behavior of proton diffusion coefficient in sulfonated co‑polynaphthoyleneimide membranes measured by 1H NMR diffusometryстатья
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Аннотация:Proton diffusion in the co-PNIS85/15 membrane was investigated in the temperature range from 200 to 363 K at differentwater contents (4 ≤ λ ≤ 21) using 1H SFG NMR diffusometry. At high hydration values, above the threshold value λ0 = 10.5,the ln(DNMR(1/T)) dependences show two different activation modes, separated by a crossover point Tcr ≈ 250–260 K. Attemperatures above Tcr, the activation energy is Ea ~ 0.20 eV, which is close to the value for bulk water (Ea ~ 0.17 eV). Attemperatures below the crossover point, the ln(DNMR(1/T)) dependences for different water contents merge together intoone straight line characterized by a much higher Ea = 0.46 eV. At low hydration values λ < λ0, the activation energies forthe high-temperature and low-temperature modes converge, so that at λ = 4, the dependence ln(DNMR(1/T)) is described byone straight line throughout the studied temperature range with Ea = 0.38 eV. A model is proposed that phenomenologicallydescribes the diffusion in the co-PNIS membrane at different moisture contents λ
