Porous Hydrogels: Present Challenges and Future Opportunities

In this feature article, we critically review the physical properties of porous hydrogels and their production methods. Our main focus is nondense hydrogels that have physical pores besides the space available between adjacent cross-links in the polymer network. After reviewing theories on the kinetics of swelling, equilibrium swelling, the structure-stiffness relationship, and solute diffusion in dense hydrogels, we propose future directions to develop models for porous hydrogels. The aim is to show how porous hydrogels can be designed and produced for studies leading to the modeling of physical properties. Additionally, different methods that are used for making hydrogels with physically incorporated pores are briefly reviewed while discussing the potentials, challenges, and future directions for each method. Among kinetic methods, we discuss bubble generation approaches including reactions, gas injection, phase separation, electrospinning, and freeze-drying. Templating approaches discussed are solid phase, self-assembled amphiphiles, emulsion, and foam methods.

Automated summary

In this feature article, the physical properties and production methods of porous hydrogels are critically reviewed. The focus is on nondense hydrogels that have physical pores in addition to the space between adjacent cross-links in the polymer network. The article discusses theories on swelling kinetics, equilibrium swelling, structure-stiffness relationship, and solute diffusion in dense hydrogels, and proposes future directions for developing models for porous hydrogels. Different methods for making hydrogels with physically incorporated pores are also briefly reviewed, including bubble generation approaches and templating approaches.