Mapping the Time Development of Hydrogel Inhomogeneities using Laser Interference

Hydrogels are materials composed of inhomogeneously crosslinked polymer chains. When exposed to aqueous solutions, hydrogels can expand up to ten thousand times their dehydrated size. The inhomogeneous structure and intense swelling of these materials results in widely varying polymer chain density in hydrated states. This unique property has made hydrogels a material of interest in many fields, such as biochemistry and health care; hydrogels are used as contact lenses, tissue reinforcers, and distributors of medicine within the body. However, the nonuniform swelling of hydrogels is still widely unexplored.

To better understand the evolution of the internal polymer chain structure, our team is using Bragg scattering and coherent interference to develop a three dimensional mapping of the polymer chains in our samples. In each method, a light source is shone into a hydrogel, where it interacts with the polymer chains and scatters accordingly. The resulting interference pattern can then be analyzed to glean information about the internal spacing between polymer chains. By employing these techniques at different sizes in the swelling process, we can quantify a sample’s development. The ability to accurately study the internal configuration of hydrogels will let us explore how swelling changes in response to environmental conditions like temperature, solvent pH level, etc. Better understanding the swelling of these materials may help advance their current applications and uncover other relevant uses.