ХИМИКО - БИОЛОГИЧЕСКАЯ. 2014. № 1

ХИМИЧЕСКИЕ НАУКИ

UDC 544.773.43

E. E. Kopishev, O. E. Mukashev, V. T. Gadamurov

SWELLING KINETICS OF STIMULUS-SENSITIVE 

POLYMER HYDROGELS

This article presents the most important information on the kinetics 

of swelling of polymer gels. Together with the classical results are giver 

the modern approaches based on models with a minimum number of 

parameters. The purpose of this article is to formulate the basic concepts 

and related thermodynamics and kinetics of swelling of stimulus-sensitive 

polymer hydrogels, which will allow to evaluate the experimental data on 

low cross-link densities polymer hydrogels. More profound information 

about the different nuances of theories on swelling polymer hydrogels 

and their experimental proof can be found, for example, in the literature 

cited in the text.

For today the main approach to the description of the kinetics of the swelling of 

polymer hydrogels is the work of Tanaka and Fillmore (TF) [1], this article presents the 

process of swelling as a result of the cooperative diffusion of the polymer network in 

the solvent. This interpretation involves the presence of a solvent through a volumetric 

backflow polymeric mesh radically different approach from earlier [2], according to 

which the swelling kinetics of the crosslinked polymer is controlled by diffusion of 

individual molecules of the solvent and not the diffusion of the grid segments.

TF theory describes the case of a neutral gel spherical shape with zero modulus 

of rigidity (G = 0). It predicts that the characteristic time τ proportional to the square 

of the swelling of the linear size of the gel and cooperative diffusion coefficient, 

which is determined as D = M / ζ, where M - unilateral compression module of mesh, 

ζ coefficient of friction between the mesh and the solvent. This diffusion coefficient 

was first used in [3] to describe the dynamics of thermal fluctuations of the polymer 

concentration in the gel, which are responsible for the dynamic light scattering.

TF theory is the basis for many subsequent models. Diffusive motion of the 

grid is described in it by the equation expressing the balance of forces of friction 

and elasticity, acting on a small volume element mesh [3]:

~

σ

ζ

∇

=

∂

t

(1)