Abstract
The swelling and compression of hydrogels in polymer solutions can be understood by considering hydrogel-osmolyte-solvent interactions which determine the osmotic pressure difference between the inside and the outside of a hydrogel particle and the changes in effective solvent quality for the hydrogel network. Using the theory of poroelasticity, we find the exact solution to hydrogel dynamics in a dilute polymer solution, which quantifies the effect of diffusion and partitioning of osmolyte and the related solvent quality change to the volumetric changes of the hydrogel network. By making a dominant-mode assumption, we propose a model for the swelling and compression dynamics of (spherical) hydrogels in concentrated polymer solutions. Osmolyte diffusion induces a biexponential response in the size of the hydrogel radius, whereas osmolyte partitioning and solvent quality effects induce monoexponential responses. Comparison of the dominant-mode model to experiments provides reasonable values for the compressive bulk modulus of a hydrogel particle, the permeability of the hydrogel network, and the diffusion constant of osmolyte molecules inside the hydrogel network. Our model shows that hydrogel-osmolyte interactions can be described in a conceptually simple manner, while still capturing the rich (de)swelling behaviors observed in experiments. We expect our approach to provide a roadmap for further research into and applications of hydrogel dynamics induced by, for example, changes in the temperature and the pH.
Highlights
Hydrogels are cross-linked polymer networks which, when fully swollen, typically imbibe large volumes of water relative to their dry volume
Using the theory of poroelasticity, we find the exact solution to hydrogel dynamics in a dilute polymer solution, which quantifies the effect of diffusion and partitioning of osmolyte and the related solvent quality change to the volumetric changes of the hydrogel network
The fitted diffusion constant, most probably, pertains to a high molecular weight species of PEO 200k, the solvent quality pressure agrees with the appurtenant swelling experiment, and the bulk modulus and permeability of the hydrogel particle agree with their independent measurement introduced above [5]
Summary
Hydrogels are cross-linked polymer networks which, when fully swollen, typically imbibe large volumes of water relative to their dry volume. Fully swollen microgels were brought into a continuously flowing polymer solution, and from both phenomenological and formative poroelastic modeling of their volumetric response the diffusion constant of osmolyte inside the hydrogels, the permeability, and the bulk modulus of the hydrogel network could be inferred. Due to nonlinearities, both the phenomenological and poroelastic model were solved numerically. Using the theory of poromechanics, we propose a dominant-mode model describing the volumetric response of hydrogels for both swelling and compression in concentrated polymer solutions. The model is compared to the experiments, and the estimations for the compressive modulus, the hydrogel permeability, and the osmolyte diffusion constant are discussed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
