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The transmittance spectra in the range 1.8 < λ < 2.2 µm for DDW for the distance between the windows, L = 200 µm. The graphs are related to the times of swelling 0.5, 5, 10, 15, 20 and 25 min. The upper curve is related to the transmittance spectrum for ordinary water; the time of swelling is 0.5 min.
Source publication
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...
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Context 1
... transmittance spectra in the range 1.8 < λ < 2.2 µm for the case of swelling Nafion in ordinary water; the distance between the windows is L = 200 µm, and the curves are related to the swelling times 70, 75, 80, 85, 90, 95 and 100 min. Polymers 2020Polymers , 12, 2888 In Figure 7, we exhibit the transmittance spectra for DDW; L = 200 µm, and the swelling times 0 < t < 25 min. Here, t = 0 corresponds to the moment of filling the cell with liquid and conducting the very first measurement, which takes about 15 s, i.e., the first graph corresponds to the time t ≈ 30 s after filling. ...
Context 2
... Figure 7, we exhibit the transmittance spectra for DDW; L = 200 μm, and the swelling times 0 < t < 25 min. Here, t = 0 corresponds to the moment of filling the cell with liquid and conducting the very first measurement, which takes about 15 s, i.e., the first graph corresponds to the time t ≈ 30 s after filling. ...
Citations
... The experimental protocol is described in detail in Refs. [44,45]. In these experiments we measured the transmittance spectrum K= I/I 0 in the IR spectral range. ...
... For rougher cell windows, the time of the cavity collapse was significantly higher than for windows with high quality of polishing. These results are described in our recent papers [44,45]; we did not include these results so as not to overload the text. ...
The work reports a number of results on the dynamics of swelling and inferred nanostructure of the ion-exchange polymer membrane Nafion in different aqueous solutions. The techniques used were photoluminescent and Fourier transform IR (FTIR) spectroscopy. The centers of photoluminescence were identified as the sulfonic groups localized at the ends of the perfluorovinyl ether (Teflon) groups that form the backbone of Nafion. Changes in deuterium content of water induced unexpected results revealed in the process of polymer swelling. In these experiments, deionized (DI) water (deuterium content 157 ppm) and deuterium depleted water (DDW) with deuterium content 3 PPM, were investigated. The strong hydration of sulfonic groups involves a competition between ortho- and para-magnetic forms of a water molecule. Deuterium, as it seems, adsorbs competitively on the sulfonic groups and thus can change the geometry of the sulfate bonds. With photoluminescent spectroscopy experiments, this is reflected in the unwinding of the polymer fibers into the bulk of the adjoining water on swelling. The unwound fibers do not tear off from the polymer substrate. They form a vastly extended “brush” type structure normal to the membrane surface. This may have implications for specificity of ion transport in biology, where the ubiquitous glycocalyx of cells and tissues invariably involves highly sulfated polymers such asheparan and chondroitin sulfate.
... Полимерные мембраны из Нафиона (Nafion TM ), разработанные фирмой DuPont, интенсивно изучаются в различных областях физики, химии и водородной энергетики [1][2][3][4][5][6][7][8][9][10][11]. Нафион представляет собой полимерный (тефлоновый) каркас с подшитыми к тефлоновой основе концевыми сульфогруппами [8]. ...
... Если смочить водой образец нафиона, то сначала проявляются его гидрофобные качества -нафион сопротивляется проникновению воды внутрь и остается практически сухим. Однако спустя некоторое время (порядка 190 min [7]) начинает проявляться гидрофильная фаза и вода впитывается в мембрану. ...
Transmittance coefficient of polymer membrane "Nafion" during adsorption of methylene blue and ascorbic acid from aqueous solutions onto the membrane was investigated by infrared (IR) Fourier spectrometry. A change in the membrane color and transmittance in the IR range during swelling of the polymer in the studied solutions was found, which is associated with chemical reactions occurring in the "membrane-solution" system. It was found experimentally that the adsorption and desorption rates of distilled water, oxidized Methylene blue (Mb^+) and reduced colorless leuco-form of methylene blue (MbH^0) on the polymer membrane are close and lie within the following limits: adsorption rate 0.029-0.031 min^-1, desorption rate 0.010-0.011 min^-1. The adsorption and desorption rates of ascorbic acid from aqueous solution were 0.021 and 0.08 min^-1, respectively. During the sorption of Мethylene blue leuco-form, we detected a change in membrane color. Thus, a redox reaction occurred in the membrane. Upon prolonged drying of the membrane, due to the proton-exchange properties of the membrane, the leuco-form of methylene blue oxidized to the initial state of Mb+. This fact may indicate the manifestation of metachromatic properties of the system "Nafion - Methylene blue". The system consisting of Methylene blue adsorbed on sulfonated perfluorocarbon can be considered as a model of dehydrogenase, a biocatalyst capable of hydrogen transfer. The Nafion membrane, due to its high cationic conductivity, promotes proton transfer and thus affects the rate of redox reactions involving Methylene blue.
... At the same time, when swelling in DDW, no cavity is formed. In [27,28], it was found that the appearance of such a cavity in ordinary ...
... Studies of isotopic effects, revealed upon the soaking of Nafion, were further developed in [27]. In this work, it was found, by using the technique of Fourier transform IR spectroscopy, that the dynamics of swelling of Nafion in water in a cell of limited size (this size was essentially less compared to the size of the area, occupied with the unwound fibers in the luminescence experiments) also depends on the isotopic content of water. ...
... In [27,28], it was found that the appearance of such a cavity in ordinary water was due to the unwinding of initially hydrophobic polymer fibers toward the bulk of water. Since the size of the cell is less than the average length of unwound fibers, these fibers abut against the windows of the cell, and a field of local shear stresses arose, which, in turn, resulted in the extrusion of water molecules from the gap between the unraveled polymer fibers (i.e., a gas cavity, free of water molecules, should be formed). ...
The temporal dynamics of luminescence from the surface of Nafion polymer membranes have been studied. In fact, the polymer membrane was soaked in liquids with different contents of deuterium. The test liquids were ordinary (natural) water (deuterium content equal to 157 ppm) and deuterium-depleted water (deuterium content is equal to 3 ppm). Simultaneously with the excitation of luminescence, the Nafion plate was irradiated with ultrasonic pulses, having a duration of 1 μs. The ultrasonic waves were generated with different repetition rates and amplitudes, and irradiated the surface of Nafion in the geometry of grazing or normal incidence. Luminescence regimes were studied when the membrane was irradiated with one ultrasonic wave (one piezoelectric transducer) or two counter-propagating waves (two piezoelectric transducers). It turned out that ultrasonic waves, which fall normal to the membrane interface, do not affect the dynamics of luminescence. At the same time, in the case of ultrasonic irradiation in the grazing incidence geometry, sharp jumps in the luminescence intensity occur, and the behavior of these jumps substantially depends on the mode of irradiation: one or two piezoelectric transducers. This allows for control of the dynamics of luminescence from the polymer surface. In accordance with this model, the possibility of altering the luminescence dynamics is due to the effect of unwinding the polymer fibers from the surface toward the liquid bulk upon soaking. It is important that such unwinding does not occur in deuterium-depleted water, which was confirmed in a direct experiment with dynamic light scattering from polydisperse aqueous suspensions of Nafion nanometer-sized particles; these suspensions were prepared in ordinary water and deuterium-depleted water. Thus, ultrasonic irradiation affects the dynamics of luminescence only when Nafion is swollen in ordinary water; in the case of deuterium-depleted water this effect is missed.
... The anomalous phenomenon of the unwinding of the polymer fibers, more reminiscent of a growth of strings of giant seaweed kelp from the ocean bed, is the source of the curious exclusion zone associated with the polymer. Subsequent experiments [21] have explored the way of growing the polymer fibers. To do that, Fourier transform IR spectroscopy was used on a Nafion-membrane, on both sides of which was a fixed volume of water in a cell. ...
... If there were no collapse of the cavity, i.e., if the Nafion plate was initially completely covered with water, the average water concentration along the beam path in the cell would remain constant in time. This is true for soaking Nafion in deuterium-depleted water (DDW; see [21] for more details). For DDW the effect of unwinding polymer fibers is absent, and therefore a cavity in the cell of limited size is not formed. ...
When a membrane of Nafion swells in water, polymer fibers “unwind” into the adjoining liquid. They extend to a maximum of about ~300 �m. We explore features of Nafion nanostructure in several electrolyte solutions that occur when the swelling is constrained to a cell of size less than a distance of 300 �m. The constraint forces the polymer fibers to abut against the cell windows. The strongly amphiphilic character of the polymer leads to a shear stress field and the expulsion of water from the complex swollen fiber mixture. An air cavity is formed. It is known that Nafion membrane swelling is highly sensitive to small changes in ion concentration and exposure to shaking. Here we probe such changes further by studying the dynamics of the collapse of the induced cavity. Deionized water and aqueous salt solutions were investigated with Fourier IR spectrometry. The characteristic times of collapse differ for water and for the salt solutions. The dynamics of the cavity collapse differs for solutions prepared by via different dilution protocols. These results are surprising. They may have implications for the standardization of pharmaceutical preparation processes.
... As was shown in our works [10][11][12], the exclusion zone formation is associated with the effect of "unwinding" of polymer fibers from the membrane surface into the water bulk. Since the unwound fibers do not completely detach from the membrane surface, these fibers resemble glycocalyx (extracellular matrix)-polysaccharide fibers on the lipid bilayer of cell membrane (see, for example, [13]). ...
... In this case, a topological structure of the "hard brush" type is formed; it was shown in [10] that near the membrane surface this structure is similar to a colloidal crystal formed by negatively charged rod-like polymer particles. Additionally, in [11,12] it was shown that the area occupied by the unwound polymer depends on the deuterium content in water. In fact, for ordinary water (the deuterium content is 157 ± 1 ppm, see [14]), the size of this area is about 200 µm, which is close to the exclusion zone size. ...
... At the same time, for deuterium depleted water (DDW, the deuterium content is ≤1 ppm), the effect of unwinding is missing. In [12], it was hypothesized that Nafion membrane is similar to a cell membrane in the sense that both the cell membrane and Nafion plate in water are surrounded by a "brush" made of polymer fibers. Therefore, there is of interest to study the interaction of various amino-acids with Nafion, taking into account the unwinding effect. ...
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.
... Indeed, the structure of the channels in the bulk of polymer is similar (conditionally) to the lipid bilayer of the cell membrane, while the external structure of the polymer fibers is similar to the glycocalyx (extracellular matrix, see [15]). This analogy was developed on a qualitative level in our recent work [16]; Within the approach based on this analogy a number of features revealing at swelling of polymer membranes in water and aqueous salt solutions have been explained. Therefore, there is a natural interest in investigating the specific interaction of Nafion with deionized water and various isotonic solutions, which were subjected to the low-frequency electromagnetic irradiation. ...
... As shown in [16], a number of effects associated with the swelling of the Nafion membrane in water and aqueous solutions of salts (in [16], aqueous solutions of NaCl were studied in a wide range of concentrations) are due to the presence of a nanobubble phase in water and aqueous solutions of electrolytes (for more details see Section 4 below). Furthermore, it was found in [16] that the swelling kinetics of the Nafion membrane has a long-term relaxation effect. ...
... As shown in [16], a number of effects associated with the swelling of the Nafion membrane in water and aqueous solutions of salts (in [16], aqueous solutions of NaCl were studied in a wide range of concentrations) are due to the presence of a nanobubble phase in water and aqueous solutions of electrolytes (for more details see Section 4 below). Furthermore, it was found in [16] that the swelling kinetics of the Nafion membrane has a long-term relaxation effect. ...
The swelling of a polymer membrane NafionTM in deionized water and isotonic NaCl and Ringer’s solutions was studied by photoluminescent spectroscopy. According to our previous studies, the surface of this membrane could be considered as a model for a cellular surface. Liquid samples, in which the membrane was soaked, were subjected to preliminary electromagnetic treatment, which consisted of irradiating these samples with electric rectangular pulses of 1 µs duration using platinum electrodes immersed in the liquid. We used a series of pulses with a repetition rate of 11–125 Hz; the pulse amplitudes were equal to 100 and 500 mV. It turned out that at certain pulse repetition rates and their amplitudes, the characteristic swelling time of the polymer membrane significantly differs from the swelling time in untreated (reference) samples. At the same time, there is no effect for certain frequencies/pulse amplitudes. The time interval between electromagnetic treatment and measurements was about 20 min. Thus, in our experiments the effects associated with the long-term relaxation of liquids on the electromagnetic processing are manifested. The effect of long-term relaxation could be associated with a slight change in the geometric characteristics of bubston clusters during electromagnetic treatment.
... The exclusion zone is about 200 μm thick. As was shown in [4,5], the exclusion zone formation is related to the effect of "intergrowth" of polymer fibers from the membrane surface into the water bulk. Since the polymer fibers unwound into the liquid bulk are not completely ...
... At the same time, in deuterium-depleted water (DDW) with a deuterium content of 3 ppm, the effect of polymer fiber unwinding is zero. A hypothesis was stated in [5], according to which a Nafion membrane is similar to a cellular membrane in the sense that both cellular membrane and Nafion plate in water are surrounded by a polymer-fiber "brush". Therefore, it is of interest to study the interaction between protein particles and Nafion, with allowance for the unwinding effect. ...
The paper studies luminescence from the Nafion polymer membrane surface at its swelling in the isotonic aqueous solutions and bi-distilled water using the experimental photo luminescent spectroscopy. Liquid samples were preliminarily treated with the electric pulses with duration of 1 µs and amplitude of 0.1 V using antenna in the form of a flat capacitor. Experiments in photo luminescent spectroscopy were carried out 20 min after the electric pulse treatment. Typical luminescence intensity dependence on the membrane swelling time could be represented as the exponentially decreasing function. Characteristic decay time of the corresponding functions and stationary level of the membrane luminescence intensity depend on the electrical pulses repetition rate. The obtained dependencies could well be reproduced. However, dependence of the luminescence intensity at certain pulse repetition rates appears to be a random function, and the reproducibility is missing. It could be assumed that these stochastic effects are associated with exposure to random external force of the electromagnetic nature acting on the polymer membrane during swelling. Low-frequency pulsations of neutron stars or white dwarfs are the source of this random force according to the authors of the work. This effect is associated with depolarization during the low-frequency electromagnetic field scattering caused by the neutron stars pulsation. Depolarization effect arises due to scattering on long-living anisotropic clusters of nano-bubbles, which, in turn, are becoming anisotropic in the external field of a flat capacitor. Depolarized scattered radiation causes stochastic oscillations of the polymer fibers unwound into the bulk liquid. In this case, luminescence should also acquire the stochastic character taking into account the effect of resonant luminescence energy transfer from a donor to the luminescence acceptor
