Water swelling behavior

N. Kawasaki, T. Okada and K. Ogawara, Water swelling behavior of perfluorosulfonic membrane, Soda Enso (Soda Chlorine), 1986, 37, 374-383. 

This gjass-ceramic, containing a Sr-phlogopite main crystal phase, exhibited water swelling behavior. Following the absorption of water by the glass-... 

In the studies by Skipper et al. the number of water layers (and thus molecules) was fixed on the basis of experimental evidence consequently, the stable states or degrees of swelhng were presumed. Quite differently, Karaborni et al. [44] determined, by means of a combination of GCMC and MD, the number of water molecules directly from a series of simulations in which the distance between montmorillonite planes was varied systematically. They observed that swelling proceeded from the dry state through the formation of one, three, and then five layers of water. This is very different from the usually beheved hydration sequence from one layer to two, then to three layers, and so on, which has been intrinsically assumed by Skipper and coworkers. The authors conclude that the complex swelling behavior accounts for many of the experimental facts. This work demonstrates impressively the power of the grand canonical simulation method. 

The main property of agricultural SAH is their ability to absorb, retain in the swollen state, and then to transfer large volumes of water, in other words, their swelling behavior in a broad sense. In this section, we consider the main features of the behavior including, when necessary, some fragments of the theory of these systems and methods of their structural analysis. 

We review useful usages of a quartz crystal-microbalnce (QCM) as tool of in situ characterization of Langmuir-Blodgett (LB) films transfer ratio and water incorporation during a transfer process, swelling behavior in water subphase, and detachment at the air-water interface. 

Some gels were synthesized which underwent the phase transition twice as the solvent composition was monotonically varied from 0% to 100%. Figure 30 shows the swelling behaviors of NIPA (open circles) and acrylamide (solid circles) gels in a mixture of dimethylsulfoxide (DMSO) and water [24]. When the DMSO concentration was lower than 33%, the NIPA gel was slightly swollen. Above 33% DMSO, a discrete transition to a collapsed state occurred. However, the gel showed a discontinuous re-swelling at 90%. Such reentrant behavior has also been observed when temperature or pH were used as variables. 

Swelling equilibria obtained with the thermoshrinking /V-alkylacrylamide gels in water indicated that their phase transition behavior is strongly dependent on the hydrophobicity of the gels. In addition, the swelling behavior was shown to... 

Besides the swelling transitions, the swelling behaviors below the critical pH have been considered. In Fig. 1, we see that swelling continues to increase as pH is lowered below the transition point. This behavior is seen when the gels are immersed in citrate buffered saline, and is due to the shift in the charge on the citrate counterions. Citrate buffer has three ionizable carboxylic acid groups, with pK values in water pKj = 3.15, pK2 = 4.78 and pK3 - 6.40. (These values are somewhat lower in salt solutions.) Thus as pH is lowered, the citrate passes... 

The swelling behavior of poly(N-isopropylacrylamide) has been studied extensively [18,19]. It has been shown that this gel has a lower critical point due to the hydrophobic interaction. Such a swelling curve is schematically illustrated in Fig. 9. The gel is swollen at a lower temperature and collapses at a higher temperature if the sample gel is allowed to swell freely in water. The volume of the gel changes discontinuously at 33.6°C. The swelling curves obtained in this way correspond to the isobar at zero osmotic pressure. On the other hand, the friction coefficient is measured along the isochore, which is given in Fig. 9,... 

The phosphatidyl cholines PCs used in this study were obtained from the Sigma Chemical Co. The DPPC used here showed swelling behavior in CaCl2 solutions similar to that of DPPC previously obtained from other sources (I). All lipids showed less than 1% impurity by thin-layer chromatography (TLC). Water was doubly distilled and salts were of reagent grade. Dextran was obtained from Pharmacia Chemicals and mixed in known proportions with salt solutions prior to contact with lipid. 

On ammonia treatment, the gross swelling behavior and changes in the strength and the structure of wood are very similar to those observed during and after steaming of wood with water vapor. The changes described below refer to wood saturated with ammonia. 

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