8 - Equilibrium and transient swelling of soft and tough pH-sensitive hydrogels: constitutive modeling and FEM implementation

Abstract

Hydrogels are classified as soft, smart materials which typically can swell up to 1000 times of their initial state. Due to their attractive properties, they are involved in many engineering devices and natural phenomena. In this chapter, as the first step, a stationary (equilibrium) model is developed to continuously predict swelling response of pH/temperature sensitive PNIPAM hydrogels. In the second part of this chapter, a coupled electro-chemo-mechanical transient large deformation swelling theory is developed for pH-sensitive hydrogels. In the third part of this chapter, we deal with tough pH-sensitive hydrogels and develop a transient electro-chemo-mechanical theory for swelling and mechanical behavior of tough pH-sensitive hydrogels. All these theories are implemented into finite element frameworks, and experimental data are used in order to validate the relevant theory. The simulations match closely the experimental data, which show the accuracy of the proposed theories and the capabilities of the proposed formulations and well as their numerical counterparts.