Equilibrium swelling degree

In contrast to polyelectrolyte hydrogels, nonionic ones are almost insensitive to the ionic composition of the medium. In particular, the equilibrium swelling degree of a charge-free PAAm gel practically does not depend on the Cu2 + concentration (Fig. 4, curve 0) nor on the concentration of several other ions or on the pH value [101]. 

Osmotic deswelling experiments, performed with a series of PAAm [20] and PVA [112] gels have revealed a correlation between their sensitivity to the external pressure and the equilibrium swelling degree in the absence of external forces. This fact is illustrated below ... 

In connection with the thermodynamic state of water in SAH, it is appropriate to consider one more question, i.e., their ability to accumulate water vapor contained in the atmosphere and in the space of soil pores. It is clear that this possibility is determined by the chemical potential balance of water in the gel and in the gaseous phase. In particular, in the case of saturated water vapor, the equilibrium swelling degree of SAH in contact with vapor should be the same as that of the gel immersed in water. However, even at a relative humidity of 99%, which corresponds to pF 4.13, SAH practically do not swell (w 3-3.5 g g1). In any case, the absorbed water will be unavailable for plants. Therefore, the only real possibility for SAH to absorb water is its preliminary condensation which can be attained through the presence of temperature gradients. 

The equilibrium swelling degree is the most important property of a hydrogel it directly influences the rate of water sorption, the permeability to drugs, and the mechanical strength of the gel. It also affects the biocompatibility of the... 

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 2 Equilibrium swelling degree of gels as predicted by Eq. (9). Z is the average number of repeat units between cross-links (Z lpxVm)-...

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

Fig. 33. Equilibrium swelling degree of d/do of copolymer gels made of various molar ratios of acrylic acid and MAPTAC in water as a function of pH at 25 °C. Acrylic add ami MAPTAC ratios of the gels are indicated in the diagram. For some gels there appear multiple phases for the same value of pH. They are reached by varying pH through different paths...

Fig. 34. Equilibrium swelling degree d/d erf copolymer gel made of 460 mM of acrylic acid and 240 mM of MAPTAC as a function of temperature at pH 7.2 (rightX and pH dependence (left) taken from Fig. 35...

Another possible choice for the reference state is the equilibrium swelling degree of the network. In that case the thermodynamic characteristics of the actual polymer-swelling solvent system would be taken into account. However this choice does not consider the conditions of network formation. Moreover when the gel is swollen to equilibrium, the elastic chains are extended with respect to the corresponding free chains, and the extension ratio is not easy to evaluate13. ... 

From Eq. (11), and taking into account the expression v = (M F02)-1, valid for ideal networks, it can be seen that the analytical relationship between the equilibrium swelling degree Q and the molecular weight M of the elastic chains is rather complicated. Several additional points have to be considered ... 

Fig. S (b). Equilibrium swelling degrees Q of polydimethylsiloxane (PDMS) networks in heptane vsAf3/5 (Jf in g mol-1)...

Table 2. Synthesis conditions and equilibrium swelling degrees of PVME gels made by -/-irradiation of aqueous solutions containing 30 wt % PVME and 15 wt % ferric oxide. Reprinted from Polymer (1991) 33 990 by permission of the publishers, Butterworth Heinemann [46]...

Linear and cross-linked poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride 19b have been investigated in aqueous solution for their interaction with K3[Fe(CN)6] and K4[Fe(CN)6] [71], In Fig. 5-5 the dependences of the equilibrium swelling degree of different cross-linked hydrogels on the... 

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