Natural Polymer‐Based Cryogels—Synthesis, Properties, and Applications: A Review

ABSTRACT Polymeric gels are 3D, crosslinked networks synthesized from a binary system consisting of a polymer and a solvent. These materials represent a significant application of functional polymers and are categorized based on their processing methods and structural characteristics into types such as hydrogels, cryogels, aerogels, and xerogels. Cryogels are macroporous networks formed through the cryotropic gelation (freezing and subsequent thawing) of aqueous polymer solutions. Unlike traditional gels, their unique interconnected macroporous architecture provides superior mechanical performance. Specifically, cryogels exhibit high elasticity and enhanced structural integrity, allowing them to withstand significant deformation without collapsing. Cryogels exhibit exceptional functional properties, including rapid responsiveness to environmental stimuli and high osmotic stability despite their highly porous architectures. The primary distinction between cryogels and other porous materials such as hydrogels, aerogels, and xerogels lies in the synthesis mechanism. While traditional hydrogels often possess nanoporous structures, cryogels are defined by a macroporous framework formed via ice templating. During the controlled freezing step, the solvent (typically water) crystallizes; these crystals act as “porogens,” displacing the polymer chains into a concentrated microphase where crosslinking occurs. Upon thawing, the removal of these crystals leaves behind a system of interconnected macropores. In contrast to synthetic cryogels, which may require harsh chemical reagents and nonrenewable precursors that contribute to environmental pollution, biobased cryogels offer a sustainable alternative. Derived from renewable natural sources, these materials leverage the inherent biocompatibility and regulated degradation rates of biopolymers. Through the crosslinking of natural scaffolds, porous structures with high water content and superior interconnectivity are achieved. Consequently, biobased cryogels have emerged as viable candidates for advanced biomedical applications, including drug delivery systems, wound dressings, and medical implants. This review summarizes recent developments in biobased cryogels synthesized from diverse natural resources including starch, cellulose, lignin, chitosan, and various proteins—and evaluates their end‐application‐based properties.