Ionic gels

Complicated theories of ionic gel swelling [99, 113, 114] must inevitably take into account the real electrostatic interactions, the finite extensibility of chains, as well as the electrostatic persistence length effect. Their application is most advisable in the case of strongly charged hydrogels [114]. 

The exchange of ions and solvent between a swollen ionic network and the surrounding electrolyte is represented in Fig. 136, where the fixed ion is taken to be a cation. It is apparent that the equilibrium between the swollen ionic gel and its surroundings closely resembles Donnan membrane equilibria. 

Fic. 136.—Diagram of swollen ionic gel in equilibrium with electrolyte solution. Fixed charges are represented by [T. ... 

Stationary phase Liquid, solid Ionic gel, cross-linked liquid Bonded phase Polar vs. nonpolar... 

J Rieka, T Tanaka. Swelling of ionic gels Quantitative performance of the Donnan theory. Macromolecules 17 2916-2921, 1984. 

T Tanaka, D Fillmore, ST Sun, I Nishio, G Swislow, A Shah. Phase transitions in ionic gels. Phys Rev Lett 45 1636-1644, 1980. 

I Ohime, T Tanaka. Salt effects on phase transition of ionic gels. J Chem Phys 11 5725-5729, 1982. 

Complex Deformation of Ionic Gels in Electric Fields. 143... 

It is notable that the structure factors, proportional to the scattered intensity, for gels could be very different between gels composed of non-ionic neutral polymers and of ionized polymers. In the case of the non-ionic gels, the structure factor is characterized by the screening length of the polymer chains, which is the so-called correlation length, On the other hand, an additional screening... 

The scattered intensity increases with increasing temperature as shown in Fig. 10. The scattered intensity diverges at the spinodal temperature, Ts in this particular case Ts = ca. 34.6 °C. Experimentally such a divergence cannot be expected because a macroscopic phase separation occurs and the scattered intensity remains finite. It is worthy to note that the difference in the scattered intensities between at 34.6 °C and at 35.0 °C clearly indicates that the system undergoes a transition. The critical phenomena of the volume phase transition of non-ionic gels with respect to temperature will be discussed in Sect 5.4. 

According to the Borue and Erukhimovich theory for polyelectrolyte solutions [84], the scattered intensity function for ionic gels may be given by the... 

Tanaka et al. found a critical point at the zero-osmotic pressure condition in ionic gels by varying the degree of ionization and diminishing the volume-discontinuity at first-order changes. At such a critical point, the first three derivatives of F with respect to V should vanish from Eqs. (2.6) and (2.26). On the other hand, the so-called spinodal point is given by K = 0, at which the volume fluctuations diverges as shown by Eq. (2.10). 

This relation is analogous to the equation of state for spin systems in the famous Landau theory of phase transitions. It reads, H = A0(T — Tc)t]/ + u0ij/3, where H is a magnetic field and i// is an order parameter, A0 and u0 being constants. In our problem, the left hand side of Eq. (2.41), which is a function of T and corresponds to H in spin systems. On the right hand side, the coefficient Vic — Vi which is determined by the degree of ionization, corresponds to the temperature parameter A0(T — Tc) in spin systems. Therefore, at yt = yu, we find T — Tc cc — c a with 8 = 3 near the critical point of ionic gels, where T— Tc plays the role of H in spin systems. 

Salt Effects on the Phase Transition in Non-Ionic Gels. 226... 

Using the Flory-Huggins derivation, the phase transition of non-ionic gels can be described by Eq. (1). In the present case, the equation includes two variables of and AF. In order to know the effect of the salt molality on < >, it is necessary... 

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