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Abstract

Organic hydrogels are composed of an organic liquid phase in a three-dimensional network through polymerization. Hydrogels have been widely used in various applications, such as super insulators, smart drug delivery systems, and even biosensors. However, controlling hydrogel properties has continued to be a challenge in the materials engineering world. In theory, the combination of adding the cryoprotectants and eutectic solvents and then freeze-drying the hydrogels would result in the perfect gel. Freeze-drying organic hydrogels could result in an unusual combination of properties, including low density, low thermal conductivity, high surface area, and high porosity. The objective was to determine a mixture of cryoprotectants and/or eutectic liquids to form smaller pores in freeze-dried organogels, while maintaining a stable structure. The gels were synthesized with acrylamide (Am), methylenebisacrylamide (MBA), and ammonium persulfate (APS). Complete polymerization occurred within 24 hours, and samples were solvent exchanged with cryoprotectants/eutectics. Of all the solutions tested, a low concentration of 5w/v % ammonium carbonate (AC) resulted in a smaller pore size of approximately 30 μm. Minimizing the pore size increases the porosity within the foam, thus allowing the material to develop its remarkable properties of low density and high porosity. There are a wide range of possibilities for fully increasing the porosity, thus improving its properties. With further investigation of different cryoprotectants/eutectic mixtures, it was determined that the architecture of organic hydrogels can eventually be easily controlled and modified based on the intended application.

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