Swelling of gel

The swelling of gels is markedly affected by the presence of electrolytes, this effect being a minimum at the isoelectric point of the material. In general, sulphates, tartrates, etc. inhibit swelling, while iodides and thiocyanates promote the swelling. Thus gelatine disperses completely in iodide solution even at low temperatures. 

T Tanaka, DJ Fillmore. Kinetics of swelling of gels. J Chem Phys 70 1214-1218, 1979. 

Substrate present —> enzymatic conversion —> product changes swelling of gel —> change in release of drug... 

The kinetics of swelling of gels is successfully described in the collective diffusion of equation which was discussed in Sect. 3.1. In the case of the swelling of... 

Flory [3] formalized the equation of state for equilibrium swelling of gels. It consists of four terms the term of rubber-like elasticity, the term of mixing entropy, the term of polymer solvent interaction and the term of osmotic pressure due to free counter ions. Therefore, the gel volume is strongly influenced by temperature, the kind of solvent, free ion concentrations and the degree of dissociation of groups on polymer chains. 

Enzyme-substrate Hydrogel containing immobilized enzymes Substrate present, enzymatic conversion, product changes, swelling of gel, release of drug... 

The investigation of the temperature effect also confirms the above interpretation of the results a rise in temperature which causes an increase in the thermal motions also causes a decrease in the convexity or concavity of the curve. Here we shall not go into the connexion between the polarity of the molecule and other physicochemical properties such as volumetric relationships, surface tension, c. We would merely refer the reader to papers by W. Ost-wald and his pupils in which the relationships between flocculation phenomena, changes in the degree of dispersion, swelling of gels, and polarity are discussed. 

Mechanism of Gel Dilation by Photoirradiation The swelling of gels with fixed charges in the network can be quantitatively understood by the osmotic pressure differentials obtained from Donnan equilibrium(22,23). The equilibrium value of the volume... 

Sofia P, Fiilber C, Demco DE, Bliimlich B, Spiess FTW (1996) Effect of residual dipolar interactions on the NMR relaxation in cross-linked elastomers. Macromolecules 29 6222-6230 Suzuki M, Hirasa O (1993) An approach to artificial muscle using polymer gels formed by microphase separation. Adv Polym Sci 110 241-261 Tanaka T, Fillmore DJ (1979) Kinetics of swelling of gels. J Chem Phys 70 1214—1218 Tanaka T, Hooker LO, Benedek GB (1973) Spectrum of light scattered from a viscoelastic gel. J Chem Phys 59 5151-5159... 

Suzuki H, Tokuda T, Kobajashi K (2002) A disposable intelligent mosquito with a reversible sampling mechanism using the volume-phase transition of a gel. Sens Actual B 83 53-59 Tanaka T (1978) Collapse of gels and critical endpoint. Phys Rev Lett 40 820-823 Tanaka T, Fillmore DJ (1979) Kinetics of swelling of gels. J Chem Phys 70 1214—1218 Tanaka T, Nishio I, Sun ST, Ueno-Nishio S (1982) Collapse of gels in an electric field. Science 218 467-469... 

Figure 2. Equilibrium swelling of gel in a 0.26M KBrOs at various pH, adjusted using H2SO4 and NaOHsolutions.. (Reproducedfrom reference 7 by permission of The Royal Society of Chemistry on behalf of the PCCP Owner Societies)...

Step I The interactions between the plasticizer and PVC resin begin, provoking a pronounced increase in both moduli, due to dissolution of easier dissolving resin (i.e., the outer layers of big particles and the small particles) and swelling of gel particles, which may begin to contact each other. 

It would seem that the osmotic nature of the swelling of gelatin, as affected by acids, is rather well established This is not surprising, since the swelling of gels without electrolyte... 

The Hofmeister series was introduced in a study of the swelling of gels in solutions. This usually occurs with evolution of heat. J. Mellanby found that the solution of globulin by a neutral salt is due to its free ions. Ions of equal valencies, whether positive or negative, are equally efficient, and the efficiencies of ions of different valencies are directly proportional to the squares of their valencies (see p. 683). 

Britton et al. (1979) have shown that cither compression or. swelling of gel may occur in the NP+L.M VL systems with specific intercictions under stress. The specific, interactions have been fixed and very carefully analyzed on the basis of the theory with the model of (laussian network chains with the (network PVA)+waler system as an example, upon tension. 

For useful application therefore it is essential for gel-type resins to swell in the reaction medium. This automatically limits their use to such media. In contrast, macroporous resins will sorb essentially all solvents into their pore structure, and so the same restriction on the reaction medium does not apply. The necessary swelling of gel-type resins also results in them being compressible. While this can be advantageous in minimising mechanical attrition in batch reactions it can present back-pressure problems when the resins are used in columns. Macroporous species on the other hand are fairly rigid, and change their total volume only marginally... 

The main characteristic of the swelling of gels is the large dependence of swelling rate on gel size. Because from Eq. (16),... 

---