Rheological Effects on Swelling of Polymer Membranes in Water

The study focuses on rheological effects which appear during swelling of the Nafion proton-exchange membrane in cuvettes of different thicknesses, and explains the effects by the appearance of the so-called excluded zone near the membrane surface. The excluded zone is the polymer fibers of the Nafion membrane, deployed towards bulk water. The depth of fiber penetration into the volume or the size of the excluded zone depends on the deuterium content in the water. It should be noted that in the process of swelling of the Nafion membrane plate in water it is structurally rearranged, which leads to a transition from a hydrophobic state to a hydrophilic one. By means of experimental methods based on Fourier transform infrared spectrophotometry, the study shows that the swelling of the Nafion membrane plate, which is initially hydrophobic, in ordinary water (deuterium content is 157 ppm) and in deuterium-depleted water (deuterium content is 1 ppm) in a cuvette of limited volume occurs differently. Small changes in the deuterium content in water turned out to lead to significant differences in the dynamics of swelling of the polymer membrane. For a 175-micron-thick Nafion membrane plate, this effect is most evident when the distance between the cuvette windows is L = 200 microns

References

[1] Mauritz K.A., Moore R.B. State of understanding of Nafion. Chem. Rev., 2004, vol. 104, iss. 10, pp. 4535--4586. DOI: https://doi.org/10.1021/cr0207123

[2] Liu L., Chen W., Li Y. An overview of the proton conductivity of Nafion membranes through a statistical analysis. J. Membr. Sci., 2016, vol. 504, pp. 1--9. DOI: https://doi.org/10.1016/j.memsci.2015.12.065

[3] Wang Y., Chen K.S., Mishler J., et al. A review of polymer electrolyte membrane fuel cells: technology, applications, and needs on fundamental research. Appl. Energy, 2011, vol. 88, iss. 4, pp. 981--1007. DOI: https://doi.org/10.1016/j.apenergy.2010.09.030

[4] Pollack G.H. The fourth phase of water. Ebner and Sons, 2013.

[5] Ninham B.W., Lo Nostro P. Molecular forces and self assembly: in colloid, nano sciences and biology. Cambridge Molecular Science. Cambridge Univ. Press, 2010.

[6] Chai B.-H., Zheng J.-M., Zhao Q., et al. Spectroscopic studies of solutes in aqueous solution. J. Phys. Chem. A, 2008, vol. 112, iss. 11, pp. 2242--2247. DOI: https://doi.org/10.1021/jp710105n

[7] Kitadai N., Sawai T., Tonoue R., et al. Effects of ions on the OH stretching band of water as revealed by ATR-IR spectroscopy. J. Solution Chem., 2014, vol. 43, no. 6, pp. 1055--1077. DOI: https://doi.org/10.1007/s10953-014-0193-0

[8] De Almeida S.H., Kawano Y. Ultraviolet-visible spectra of Nafion membrane. Eur. Polym. J., 1997, vol. 33, iss. 8, pp. 1307--1311. DOI: https://doi.org/10.1016/S0014-3057(96)00217-0

[9] Bunkin N.F., Lyakhov G.A., Kozlov V.A., et al. Time dependence of the luminescence from a polymer membrane swollen in water: concentration and isotopic effects. Phys. Wave Phen., 2017, vol. 25, no. 4, pp. 259--251. DOI: https://doi.org/10.3103/S1541308X18010107

[10] Bunkin N.F., Shkirin A.V., Kozlov V.A., et al. Near-surface structure of Nafion in deuterated water. J. Chem. Phys., 2018, vol. 149, iss. 16, art. 164901. DOI: https://doi.org/10.1063/1.5042065

[11] Bunkin N.F., Balashov A.A., Shkirin A.V., et al. Investigation of deuterium substitution effects in a polymer membrane using IR Fourier spectrometry. Opt. Spectrosc., 2018, vol. 125, no. 3, pp. 337--342. DOI: https://doi.org/10.1134/S0030400X18090072

[12] Bunkin N.F., Kozlov V.A., Shkirin A.V., et al. Dynamics of Nafion membrane swelling in H2O/D2O mixtures as studied using FTIR technique. J. Chem. Phys., 2018, vol. 148, iss. 12, art. 124901. DOI: https://doi.org/10.1063/1.5022264

[13] Workman Jr. J., Weyer L. Practical guide and spectral atlas for interpretive near-infrared spectroscopy. CRC Press, 2012.

[14] Gebel G. Structural evolution of water swollen perfluorosulfonated ionomers from dry membrane to solution. Polymer, 2000, vol. 41, iss. 15, pp. 5829--5838. DOI: https://doi.org/10.1016/S0032-3861(99)00770-3

[15] Furst E.M., Squires T.M. Microrheology. Oxford Univ. Press, 2017.

[16] Craig H. Standard reporting concentrations of deuterium and oxygen-18 in natural water. Science, 1961, vol. 133, iss. 3467, pp. 1833--1834. DOI: https://doi.org/10.1126/science.133.3467.1833