FOAM-TEMPLATED POROUS HYDROGELS: TUNING STRUCTURE AND WATER UPTAKE KINETICS

Abstract

Foam templated porous polymers, which are also called polyfoams, have applications in food packaging, energy storage, sustainable agriculture, and plant growth in outer space. These materials are highly versatile due to their lightweight properties and tunable mechanical characteristics. Despite their advantages, polyfoams face challenges such as low water uptake and foam stability issues, where controlling foam stability prior to polymer network formation remains a challenge that limits further scientific exploration in this field. Achieving small pore sizes (less than 100 µm) is crucial for enhancing properties like thermoresponsiveness and water uptake kinetics. Another key challenge is controlling porosity to fine-tune the hydrogels for specific applications. This study explores the interactions between the block copolymer Pluronic F68 Diacrylate (PF68DA) and sodium dodecyl sulfate (SDS), which are used as the macromer and co-surfactant in the precursor, respectively. The goal is to understand how SDS influences foam stability and interfacial dynamics and how these factors affect the final porosity and properties of polyfoam hydrogels obtained from the crosslinking of PF68DA. Our findings reveal that SDS reduces both pore (also known as void) and pore throat (also known as window) sizes in the resultant porous hydrogels. At elevated SDS concentrations, destabilization occurs due to increased depletion attraction forces, leading to the formation of more windows with smaller void sizes in the final hydrogel structure. While these hydrogels exhibit lower mechanical strength compared to non-porous hydrogels, their mechanical properties remain comparable to polyfoams reported in literature. Additionally, this research further confirms that introducing foaming significantly enhances thermoresponsiveness and water uptake kinetics compared to non-foamed (i.e., dense) hydrogels.