Eur. Phys. J. E (2014) 37: 93
https://doi.org/10.1140/epje/i2014-14093-2

Regular Article

Swelling of thermo-responsive hydrogels

Center for Plastics Technology, Danish Technological Institute, Gregersensvej 7, 2630, Taastrup, Denmark

^* e-mail: add@teknologisk.dk

Received: 30 May 2014
Revised: 10 September 2014
Accepted: 17 September 2014
Published online: 22 October 2014

Abstract

A model is developed for the elastic response and solvent diffusion through a thermo-responsive gel under an arbitrary deformation with finite strains. The constitutive equations involve the stress-strain relation, the nonlinear diffusion equation for solvent molecules, the heat conduction equation, and the Allen-Cahn equation for an order parameter (proportional to the concentration of hydrophilic segments in polymer chains). Material constants are found by fitting swelling diagrams for PNIPA gels under uniaxial tension. Numerical analysis demonstrates good agreement between predictions of the model and observations in tests with stress- and strain-controlled programs.