The stress diffusion coupling in the swelling dynamics of cylindrical gels

Continuum mechanical model is proposed for dynamical processes in gels that involve coupling between the elastic deformation and solvent permeation. Basic equations are derived by two methods, by a physical argument, and by a variational principle. The model is then applied to discuss the swelling of gels, in which solvent permeation causes deformation, and the squeezing of gels, in which mechanical force induce solvent permeation. The model is also applied to the dynamics of the volume transition of gels. It is shown that the elasticity of gels creates various unusual features in the phase transition dynamics.

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“…A rigorous result has been obtained only recently. 34) Leaving the detail to, 34) we here summarize the main result.…”

Section: Swelling Of a Cylindrical Gelmentioning

confidence: 99%

Gel Dynamics

2009

Self Cite

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“…Furthermore, u z (r,h,z,t) is independent of r and h, is proportional to z, and is written as a(t)z, with a(t) being a variable to be determined. 39 For these deformations, the off-diagonal components of the stress tensor r, r ij , i = j, are deduced to be trivial. As a result, from the h and z components of Eq.…”

Section: Problem Formulationmentioning

confidence: 99%

“…The stress diffusion coupling model 38,39 accounts for force balance on the hydrogel and solvent diffusion in the hydrogel. The force balance is…”

Section: Problem Formulationmentioning

confidence: 99%

Drug loading into and drug release from pH‐ and temperature‐responsive cylindrical hydrogels

Ninawe

Parulekar

2011

Biotechnology Progress

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Hydrogels that undergo deformation upon appropriate changes in pH or temperature have considerable promise as drug delivery vehicles. Drug uptake in swelling and nonswelling cylindrical hydrogels and drug release from these into a target fluid are investigated here. A mathematical model for hydrogel-solution composite, a composite of a distributed parameter system (cylindrical hydrogel) and a lumped parameter system (surrounding solution), is developed. The polymer network displacement in a swelling/deswelling hydrogel is described by a stress diffusion coupling model. The analytical solution for network displacement is used to predict solvent intake by swelling hydrogels, solvent efflux from deswelling hydrogels, and changes in pressure, porosity, and effective drug diffusivity. These in turn influence drug uptake during and after hydrogel swelling and drug release from hydrogel during and after deswelling. Numerical results illustrate benefits of hydrogel swelling for drug loading and merits of different modes of drug release. Drug uptake and drug release by temperature-responsive hydrogels are compared with those by hydrogels not subject to deformation.

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“…The hydrogel is considered to be a poroelastic medium and its free deswelling is described by the model of Yamaue and Doi (2005). The displacement vector, u, satisfies the equations…”

Section: Deswelling Modelmentioning

confidence: 99%