Kinetics of thermally induced swelling of hydrogels

Abstract

We present a continuum model for thermally induced volume transitions in stimulus-responsive hydrogels (SRHs). The framework views the transition as proceeding via the motion of a sharp interface separating swollen and collapsed phases of the underlying polymer network. In addition to bulk and interfacial force and energy balances, our model imposes an interfacial normal configurational force balance. To account for the large volume changes exhibited by SRHs during actuation, the governing equations are developed in the setting of finite-strain kinematics. The numerical approximations to the coupled thermomechanical equations are obtained with an extended finite element/level-set method. The solution strategy involves a non-standard operator split and a simplified version of the level-set update. A number of representative problems are considered to investigate the model and compare its predictions to experimental observations. In particular, we consider the thermally induced swelling of spherical and cylindrical specimens. The stability of the interface evolution is also examined.

Generalized finite element enrichment functions for discontinuous gradient fields

“…The mesh independence that the method provides plays a fundamental role in problems that require complete remeshing or even refinement around areas of interest inside the problem domain. The problems addressed by the GFEM include structural problems [10,11], crack propagation in fracture mechanics [12][13][14][15][16] and phase interface/change problems [17][18][19][20].…”

Stretching and polarizing a dielectric gel immersed in a solvent

“…Lai et al (1991) extended the theory to include the effects of ions and electric fields. More recent work has been reported by, among many others, Durning and Morman (1993), Dolbow et al (2004), Ji et al (2006), Korchagin et al (2007), Tsai et al (2004), andLi et al (2007a,b). Qi (2007) has led an online discussion on the mechanics of gels.…”

Study of swelling behavior of temperature sensitive hydrogels considering inextensibility of network

“…Considering a sharp front separating swelled and collapsed phases, Ji et al [29] developed a constitutive model in the scope of extended finite element method for thermally induced volume transitions in stimulus-responsive hydrogels. Birgersson et al [27] derived a model for transient behavior of a temperature sensitive hydrogel by employing a biphasic approach.…”