Swelling pressure, osmotic

Fig. 4 Insert Representative macroscopic image of an APNP hydrogel scaffold seeded with human adipose-derived stem cells following 7 days of culture in a 12-well plate. Graph Osmotic swelling pressure profile of APNP hydrogel scaffolds (green-squares) compared to human NP (orange-triangles and red-diamonds) values found in the literature [28]...

We have also shown that these scaffolds generate an osmotic swelling pressure profile (Fig. 4) that mirrors that of a 25-year-old human and that they are conducive to repopulation with human ADSC [28, 113]. 

Ionizable groups incorporated in the chain dissociate into fixed charges and counterions, whose existence causes osmotic swelling pressure, give rise to the swelling of the gel. We assumed the following equation based on the van t Hoff equation ... 

Figure 12. Hypothetical increase in the internal osmotic swelling pressure, II, and counteractive polymer matrix elasticity (reflected in an increasing cohesive energy density, E), with increasing water content, n. n0 is the number of moles of water, per ionic sidechain, for which Tl-E = 0 (24).

Han, E.H., Chen, S.S., Klisch, S.M., Sah, R.L., 2011b. Contribution of proteoglycan osmotic swelling pressure to the compressive properties of articular cartilage. Biophys. J. 101, 916-924. 

The glucose-induced osmotic swelling pressure of the PBA-containing, glucose-sensitive hydrogel can be measured by confining it between a porous membrane and the diaphragm of a miniature pressure transducer. In this... 

A polymer will absorb solvent until the solvent chemical potentials in the polymer (gel) phase and in the free solution are equal. This statement can be rewritten in terms of osmotic swelling pressure, which is zero at equilibrium [8] ... 

The term Iljon is the osmotic swelling pressure which exists due to a difference in mobile ion concentration between the polymer and the free solution. Since counterions arising from the dissociation of ionizable groups in the polymer must remain inside the gel to maintain electroneutrality, this term can be substantial for an ionizable polymer. Any solute that is excluded from the network either by size or by Donnan ion exclusion will cause deswelling by reducing the magnitude of this difference. If the gel is a 1 1 electrolyte and the Ions form an ideal solution, this osmotic pressure may be written as follows ... 

Direct mechanical methods can be used to determine the swelling pressure of hydrogels, e.g., by means of devices in the form of a cylindrical chamber equipped with a piston in which the gel contacts the solution through a porous membrane. This technique allows measuring very low pressure (of the order of 0.1-10 kPa) and makes it possible to analyze the SAH with swelling up to 700 ml g-1 [102, 103]. Among others, the method of osmotic deswelling is to be mentioned [104]. 

The swelling pressure or osmotic deswelling data can be, therefore, described as the functions of n(w) by either of the theories [115]. This description can be then applied to determining the network parameters (see, for example, Ref. [22]). On the other hand, the swelling pressure which is directly connected with the chemical potential of water in the gel ... 

The mechanism of action by which silane and siloxanes reduce expansion has been attributed to water repellence and air entrainment. Phosphate addition or coatings may interfere with the dissolution of silica gel and the formation of gel. It is also possible that phosphate reduces the osmotic potential and the swelling pressure in the gel. The manner in which air entrainment reduced expansion was attributed to the accommodation of alkali-silica gel in the air void system. For example, it was found that air-entrained concrete with 4% air voids could reduce AAR expansion by 40% [23]. 

Finally, several attempts have been made to develop an absolute molar mass detector based on osmotic pressure measurements. Commercially available membrane osmometers are designed for static measurements, and the cell design with a flat membrane is not suited for continuous flow operation. Different from the conventional design, Yau developed a detector which measures the flow resistance of a column caused by osmotic swelling and deswelling of soft gel particles used for the packing (see Fig. 12) [65,78]. With a microbore gel column, a... 

As can be seen from the derivation of Eq. (20), the swelling pressure ir is equivalent to the osmotic pressure developed by a non-crosslinked polymer solution of the same concentration In the absence of significant swelling, this pressure will be relatively small and to a good approximation the right hand side of Eq. (20) can be set equal to zero. Thus, a measurement of the equilibrium absorption of solvent (cfrj) yields an approximate experimental value of x p-... 

If a similar equation could be applied to the clay phase, w would represent the osmotic pressure or swelling pressure of the clay. It is possible, by monitoring the spacing between clay layers (using x-ray diffraction methods), to determine the external pressure that must be applied to a clay gel to exactly counterbalance the swelling pressure. If the applied pressure is greater than the clay s swelling pressure, the clay... 

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