Swelling isotropic

Fig. 5. Influence of pressure on swelling of two samples of partly ionized PAAm hydrogels in 0.01 N aqueous NaCl solution solid curve — uniaxial, dashed curves — isotropic swelling as obtained by calculation. Points on the y-axis correspond to the free swelling. From Dubrovskii etal. [22]...

The a used here corresponds to the isotropic swelling factor for the cross-linked gels treated in Chapter XIII. The subscript is dropped for simplicity. 

Factor expressing the linear deformation of a network structure by isotropic swelling, i.e., a = (F/Fo) = (Chap. XIII). 

R > is the mean square end-to-end distance of the polymer chain. Consider a sample stretched by a factor Ay in the Y direction and Az in the Z direction. A general deformation can be easily treated, but for simplicity only uniaxial stretching or isotropic swelling will be examined. Note that under conditions of uniaxial deformation, the volume of the sample changes very little. This change may be ignored, and it becomes convenient to set Az = A and Ax — Ay. ... 

For isotropic swelling equilibrium we find from Eq. (III-17), if we neglect the possible volume dependence of [Pg.41]

Eq. (7.43)]. Explain why the stretching caused by isotropic swelling increases the contribution to the modulus from each combined strand. Why can the elastic modulus be approximated by an elastic energy density ... 

The restraints on isotropic swelling due to coating adhesion to the substrate. 

One of the unique properties of hydrogels is that due to isotropic swelling, the original shape can be maintained during and after swelling. 

For isotropic swelling X = X = X = (( )r/( )re), where is the volume fraction of the dry elastomer and usually has a value of unity in the unswollen state, and ( )re is the volume fraction of the elastomer at the maximum degree of swelling (equilibrium) when the network is in contact with excess solvent. Also, for a phantom network. 

The way to translate these quasi-isotropic swelling and shrinking processes to a macroscopic movement was attained in 1992 by Swedish and Spanish teams independently, by the construction of... 

Ai s correspond to changes in the sample s sizes at deformation and swelling. Besides, for isotropic swelling. 

Equations (10), (38), (39) and (78) then lead to the isotropic swelling equation... 

Flory has derived the entropy change for the isotropic swelling of a rubber network ... 

The elastic Gibbs energy introduced in Chapter 4 must be extended to include the swelling deformation, since the volume of the network will now change. The deformation ratio for isotropic swelling is defined as = V/ Vq, where Vq is the volume of the dry rubber. The elastic Gibbs energy is then ... 

Such a small expansion in swelling is J so reported by Beltzung et al. for a poly(dimethylsiloxane) networks. Here again, we confirm a puzzling observation without offering any sensible explanation beyond the previous attempts to justify the observed insensitivity of chain deformation with isotropic swelling. ... 

In order to consider this low vacancy mobUity strategy for designing radiation-tolerant stmctural materials, the selected material also needs to exhibit low point defect volumetric swelling, and preferably isotropic swelling behavior in order to... 

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