Abstract
In photoluminescence spectroscopy experiments, the interaction mode of the polymer membrane Nafion with various amino-acids was studied. The experiments were performed with physiological NaCl solutions prepared in an ordinary water (the deuterium content is 157 ± 1 ppm) and also in deuterium-depleted water (the deuterium content is ≤1 ppm). These studies were motivated by the fact that when Nafion swells in ordinary water, the polymer fibers are effectively “unwound” into the liquid bulk, while in the case of deuterium-depleted water, the unwinding effect is missing. In addition, polymer fibers, unwound into the liquid bulk, are similar to the extracellular matrix (glycocalyx) on the cell membrane surface. It is of interest to clarify the role of unwound fibers in the interaction of amino-acids with the polymer membrane surface. It turned out that the interaction of amino-acids with the membrane surface gives rise to the effects of quenching luminescence from the luminescence centers. We first observed various dynamic regimes arising upon swelling the Nafion membrane in amino-acid suspension with various isotopic content, including triggering effects, which is similar to the processes in the logical gates of computers.
Highlights
NafionTM is an ionic copolymer consisting of a perfluorocarbon backbone and cross-linked terminal sulfonate groups
The amino-acids under study were characterized in dynamic light scattering (DLS) experiments at pH = 3
The weight concentration for all amino acids in these experiments was 20 g/L; such a high concentration of amino-acids in this experiment is due to the very small scattering cross section of particles, the size of which is on the order of several Angstroms
Summary
NafionTM (for more details see review [1]) is an ionic copolymer consisting of a perfluorocarbon backbone (similar to Teflon) and cross-linked terminal sulfonate groups. Nafion has high chemical and thermal stability and is being actively studied as a matrix for hydrogen fuel cells In this case, sulfonate groups have hydrophilic properties, while perfluorocarbon chains are hydrophobic ones. Nafion exhibits amphiphilic properties: various structures, consisting of hydrophilic and hydrophobic segments, are formed. These structures are highly sensitive to changing the concentration of water inside the polymer matrix, which leads to the formation of cylindrical micelles in the form of pass-through cylindrical channels. Nafion properties depend on various impurities in the system It was shown in [6] that additions of H2S of about 10 ppb to pure hydrogen resulted in a significant decrease in the proton conductivity through a polymer membrane in a hydrogen fuel cell, i.e., to a decrease in the fuel cell efficiency
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