ABSTRACT: Many stimulus responsive polymer gels operate in non-isothermal, chemically saturated environments. Such situations require not only thermo-mechanically coupling, but thermo-chemo-mechanical coupling. Thermo-chemo-mechanical coupling is a coupling between the temperature, "chemical," and deformation fields. All fields may be inhomogeneous and evolve with the system over time. The most familiar type of material coupling is thermo-mechanical coupling, between the temperature and deformation fields. What is non-standard is the “chemical coupling.” In the specific case considered in this talk, the “chemical” coupling is the diffusion of fluid into the polymer network causing large volume changes. Many continuum level theories in the literature do not fully couple the temperature, chemical, and deformation fields. Instead, they take the isothermal limit, or constant fluid concentration. We have developed a general, thermodynamically consistent, continuum level thermo-chemo-mechanically coupled theory for large deformations of polymer gels. In discussing special constitutive equations, we limit our attention to isotropic materials, and a special model for the free energy based on standard Gaussian statistical mechanics considerations of changes in the configurational entropy due to stretching of the polymer chains, along with a simple Flory-Huggins model for the free energy change due to mixing of the fluid with the polymer. Furthermore, current commercial finite element codes do not provide for a coupling between the large deformation, temperature, and chemical fields. Therefore, the corresponding numerical procedure in the context of standard finite element methods is also developed. The numerical simulation capability is then implemented for some representative examples of swelling in polymer gels due to fluid absorption.

Details:

1. 1)Shawn A. Chester and Lallit Anand, 2010. A coupled theory for fluid permeation and large deformations for elastomeric materials. Journal of the Mechanics and Physics of Solids, 58 1879-1906.
   

2. 2)Shawn A. Chester and Lallit Anand, 2011. A thermo-mechanically coupled theory for fluid permeation in elastomeric materials: Application to thermally responsive gels. Journal of the Mechanics and Physics of Solids, 59 1978-2006.
   

3. 3)Shawn A. Chester, Claudio V. Di Leo, and Lallit Anand, 2015. A finite element implementation of a coupled diffusion-deformation theory for elastomeric gels.  International Journal of Solids and Structures, 52 1-18.
   

Free Swelling

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Constrained Swelling

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Microfluidic Valves

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