Swelling curve pressure

In the polyelectrolyte regime, due to the presence of low-molecular salt, the osmotic pressure of ions becomes less pronounced because the concentration of salt within the network turns out to be less than the concentration of salt in the outer solution n [27]. As the concentration ns grows, the amplitude of the jump of the dependence a(x) decreases and the jump shifts to the region of better solvents (Fig. 2, curve 2). At some critical value of n, the jump on the curve a(x) disappears, i.e. collapse of the network becomes smooth (Fig. 2, curve 3). Under the subsequent increase of n, the curve a(x) becomes closer and closer to the swelling curve of corresponding neutral network (Fig. 2, curves 4). 

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,... 

Fig. 9. The swelling curve of the poly(/V-isop-ropylacrylamide) gel is schematically shown. The isobar curve (thick line) corresponds to the zero osmotic pressure. The dotted line indicates the experimental path at which the volume is fixed at the initial volume V0 (the volume at which the gel is prepared)...

Figure 3.5.3. Dependence of the gel osmotic pressure on i 2 ( ) and the state diagram of the NP+LMWL system at tt = 0 (6). AHDI.JM is the swelling curve. / I iCFJ is the coexistence curve of two states of gel, KGCHL is the curve at which (d7rfdv2) = 0 (Tanaka, 1979) (Reprinted from Polymer 20 (1979) 1404 1412. Copyright 1979 with kind permission of Elsevier Science - NL, Sara Burgerhartstraat 2. ). 1055 KV Amsler dam. The N elherlandsj...

Fig. 5 now shows a typical, rather linear swelling curve for the alloy NbTo,59. Only the initial slope is used for data analysis. Table 1 shows the values for (v g/J2), v g and the pressures p extracted from our swelling curves. Thus, He requires roughly half of an atomic volume when it is located in the present bubbles. The pressures obtained lie in the range 5 to 10 GPa which is close to the threshold pressure required for loop punching ... 

Fig. 4.27 Swelling and low-pressure hysteresis in the adsorption of n-butane on compacts of coal at 273 K. The following are plotted against the relative pressure (a) the amount adsorbed (b) the percentage increase on length (c) the decrease —Ajc in electrical conductivity. The curves for ethyl chloride were very similar to the above curves.

Fig. 5. Influence of pressure on swelling of two samples of partly ionized PAAm hydrogels in 0.01 N aqueous NaCl solution solid curve — uniaxial, dashed curves — isotropic swelling as obtained by calculation. Points on the y-axis correspond to the free swelling. From Dubrovskii etal. [22]...

The influence of neutral salts as well as of acids and bases on the swelling of gelatine which we have seen can be attributed to an apparent change in the solvation of the gel fibrils and may be interpreted in the light of Donnan s theory of the effect of a non-diffusible ion on the osmotic pressure differences between the two phases, is likewise to be noted in the alteration of the viscosity and alcohol precipitation values of protein solutions. From the considerations already advanced there should exist two well-defined maxima in the viscosity and alcohol precipitation curves when these properties are plotted as functions of the Ph, the maxima coinciding with the points of maximum dissociation of the salts... 

FIG. 10 Pressure curves for Na+-mica surfaces in a 2 mol/L NaCl solution calculated from Eq. (27) and converted for flat surfaces. Also represented is the swelling pressure for a Na-montmorillonite platelet system. Inset pressure curves measured using the direct force method [51]. 

Whether or not this very remarkable similarity in the curves indicates that the swelling of the charcoal really is brought about by the lateral bombardment pressure of their moving molecules, must be left to the reader to judge a priori the likelihood of the films being sufficiently mobile to do this seems rather small, but no other explanation of the similarity has yet been advanced. 

Water vapour sorption isotherms for a 10% crosslinked sulfonic acid cation exchanger and a 0.4% crosslinked reference resin are shown in Figure 5.2 together with a calculation of the swelling pressure. The anomalous relative positions of the curves at low values of relative humidity P/Pq may be explained in terms of van der Waals type intramolecular forces which weakly bind adjacent polymer chains in de-swollen exchangers of low crosslinking. 

Figure 25. Curve of swelling pressure (log scale) vs. dry-volume svecific gravity Gq (49). (Reproduced with permission from Ref. 10. Copyright 1972, Syracuse University Press.)...

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