Polyelectrolyte gel swelling

It is well known that polyelectrolyte gels swell, shrink or bend when DC electric current is applied [169]. These properties of gels are applicable for the construction of chemomechanical devices, artificial muscles, energy conversion systems etc. [170]. Osada and co-workers [171] have constructed an eel-like gel actuator on the basis of poly(2-acrylamido-2-methylpropane sulfonic acid) and studied its chemomechanical properties. Polyampholyte gel is bent to the cathode or anode side if it has predominantly negative or positive charges along the macromolecules (Fig. 39) [172]. As seen from Fig. 39, the amplitude of deflection is gradually decreased with the approach to the lEP. This is probably due to... 

The important role of counterions in the swelling of polyelectrolyte gels was established long ago. At the beginning of 1950s, Katchalsky et showed that the polyelectrolyte gel swelling is determined by a balance between the elastic energy of polymer chains and the osmotic pressure of counterions. 

The swelling pressure of polyelectrolyte gels is usually considered as a sum of the network (jtnct) and ionic contributions (nion) [4, 99, 101, 113, 114]. The former describes the uncharged gel while taking into account the interaction between the polymer segments and the solvent as well as the network elasticity [4] ... 

Siegel, R, A, Hydrophobic Weak Polyelectrolyte Gels Studies of Swelling, Equilibria and Kinetics. Vol. L 09, pp. 233-268. 

The equation for the equilibrium swelling degree is more complicated for polyelectrolyte gels—those with ionizable groups—because of the need to include the additional ion-related terms in Eq. (5). The nion term can be substantial... 

Figure 3 Equilibrium swelling degree of polyelectrolyte gels as predicted by Eq. (12).

RA Siegel. Hydrophobic weak polyelectrolyte gels—Studies of swelling equilibria and kinetics. Adv Polym Sci 109 233-267, 1993. 

Oppermann, W., Swelling Behavior and Elastic Properties of Ionic Hydrogels, in Polyelectrolyte Gels Properties, Preparation, and Applications (R. S. Harland and R. K. Prud homme Eds.), pp. 159-170. American Chemical Society, Washington (1992). 

Further progress in the field of conformational phase transition in polymer gels, especially in polyelectrolyte gels, was achieved in the paper by Tanaka [4]. He investigated the swelling of polyacrylamide (PAA) networks, which were crosslinked by N,AT-methylenebisacrylamide (BAA), in the mixtures of water and acetone. When the quality of the solvent was made poorer (this happened when the concentration of acetone was increased or the temperature was lowered) shrinking of the samples was observed. Tanaka showed that at certain... 

Hydrophobic Weak Polyelectrolyte Gels Studies of Swelling Equilibria and Kinetics... 

Aside from their potential therapeutic applications, these hydrophobic polyelectrolyte gels have proved to be interesting in their own right. We have made a rather extensive study of their equilibrium and kinetic swelling properties in response to various chemical stimuli. We have found that their behavior cannot always be explained by theories that have been put forth for more hydrophilic systems. 

In this article we review our experience with hydrophobic polyelectrolyte gel systems. In Sect. 2 we summarize the essentials of the synthesis procedure. In Sect. 3 swelling equilibrium measurements are summarized, and in Sect. 4 these measurements are used to evaluate a simple theoretical model of gel swelling. Significant quantitative discrepancies are found, the putative sources of which are discussed. Swelling and deswelling kinetics results are discussed in Sects. 5 and 6. Section 7 summarizes the article, and suggests some implications of the reported results. 

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