The swelling of a polymer ion-exchange membrane Nafion in water with various heavy isotope contents (D2O) was studied by photoluminescent UV spectroscopy. The photoluminescence arises because of the presence of sulfonic groups attached to the ends of the perfluorovinyl ether groups that form the tetrafluoroethylene (Teflon) backbone of Nafion. The width of the colloidal region, which is formed near the membrane surface as a result of the outgrowth of Nafion microfibers toward the bulk liquid, varies non-monotonically with D2O content, displaying a narrow maximum in the low concentration region. A significant insight into the unexpected isotopic effects revealed in swelling Nafion in deuterated water is provided. Mainly, the polymer swelling is very sensitive to small changes (on the order of several tens of parts per million) in the content of deuterium, which, for instance, can help in understanding the isotopic effects in living tissues.

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When Nafion swells in water, colloidal particles are repelled from the polymer surface; this effect is called the formation exclusion zone (EZ), and the EZ size amounts to several hundred microns. However, still no one has investigated the EZ formation in a cell whose dimension is close to the EZ size. It was also shown that, upon swelling in water, Nafion fibers “unwind” into the water bulk. In the case of a cell of limited volume, unwound fibers abut against the cell windows, and water is completely pushed out from the region between the polymer and the cell window, resulting in a cavity appearance. The temporal dynamics of the collapse of this cavity was studied depending on the cell size. It is shown that the cavity formation occurs due to long-range forces between polymer strands. It turned out that this scenario depends on the isotopic composition of the water, ionic additives and water pretreatment. The role of nanobubbles in the formation and collapse of the cavity were analyzed. The results obtained allowed us to conclude that the EZ formation is precisely due to the unwinding of polymer fibers into the liquid bulk.

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Objective: Methodology development for quality control of optically active pharmaceutical substances based on water isotopologues.Methods: Solutions of L-ascorbic acid, glucose, galactose and valine stereoisomers were prepared using deuterium depleted water (DDW-«light» water, D/H=4 ppm), natural deionized high-ohmic water (BD, D/H=140 ppm), heavy water (99.9% D2O). The optical rotation was observed using an automatic polarimeter Atago POL-1/2. The size distribution of giant heterogeneous clusters (GHC) of water was recorded by low angle laser light scattering (LALLS) method.Results: The infringement of Biot’s Law was found for solutions of ascorbic acid, expressed in the absence of a constant value of the specific optical rotation  at a concentration of below 0.1%, depends on the D/H ratio. The inequality was established in absolute values of optical rotation for L-and D-isomers of valine in solutions with different ratios of hydrogen isotopologues. The mutarotation of glucose confirmed the first-order kinetics, and the activation energies were statistically distinguishable for BD and DDW. The mutarotation of the natural galactose D-isomer proceeded with a lower energy consumption compared to the L-isomer. In heavy water, the mutarotation of monosaccharides had different kinetic mechanisms. Polarimetric results correlated with the number and size of GHC, which confirmed the possibility of chiral solvent structures induction by optically active pharmaceutical substances.Conclusion: In the optically active pharmaceutical substances quality control there should be considered the contribution of induced chiral GHC of water to the optical rotation value that depends on the isotopic D/H ratio, the substance nature and the form of its existence at a given pH.