2022 Annual Meeting
Reversible CO2-Controlled Volume Phase Transitions and Swelling in Hydrogels
Smart materials are often inspired by systems or processes in nature which respond to environmental stimuli. CO2 has garnered interest as a stimulus as it is abundant, inexpensive, and non-toxic. Swelling, or the process of absorbing water, is a fundamental property of hydrogels yet is often not controlled using an environmental stimulus. In this work, CO2 is used to trigger pronounced, reversible swelling of a crosslinked hydrogel. Specifically, CO2 responsivity was conferred to hydrogels with a volume phase transition temperature (VPTT), which demarcates the transition from a collapsed to a swollen state. We show that these gels display a CO2-switchable volume phase transition that enables isothermal gas-triggered swelling. Compositional studies were conducted to determine the effect of varying co-monomer content on the resulting VPTT shifts in these samples. Increasing the concentration of the CO2-responsive moiety resulted in an increase in the initial VPTT as well as a greater shift in the VPTT after CO2 exposure. Isothermal swelling studies were conducted at a temperature between the VPTTs before and after CO2 exposure. These studies show that CO2 triggers a reversible volume transition and controls the extent of swelling. The results presented here demonstrate the promise of CO2 as a stimulus for the design and study of smart materials, which are suitable for applications in drug delivery, microfluidics, and soft actuators.