Superabsorbent Core/Shell Composite Materials: A Review on Synthesis, Design and Applications

Superabsorbent core/shell composite materials are a type of advanced materials presenting enhanced water absorption and retention capabilities. The central core material can swell and absorb water covered by a shell that serves a specific function. The composition and functionality of each layer can be tailored to improve the material's performance. The core is typically fabricated from superabsorbent polymers such as sodium polyacrylate, poly(acrylic acid) or other hydrophilic materials. The shell can be either inorganic polymers or organic polymers such as poly(methyl methacrylate), biodegradable polymers, polysaccharides or other functionalized materials in order to enhance biodegradability, mechanical strength or responsiveness to stimuli (e.g., temperature, pH). These materials present enormous potential to address issues for versatile applications in various fields, including biomedical applications, hygiene products and agriculture, due to their tailored structure. The common synthesis techniques for these advanced materials are emulsion polymerization, in situ polymerization, suspension polymerization with respect to the core material, layer-by-layer assembly and the sol-gel technique with respect to the shell formation. The techniques that are usually utilized for the characterization of the aforementioned materials and the validation of their functionalities are based on thermal analysis, morphology studies and swelling behavior and water retention and release mechanical properties, respectively. This review offers an in-depth examination of recent advancements in synthesis methods, structural engineering approaches and emerging applications of superabsorbent core/shell composites, highlighting the critical importance of material design in boosting their performance and broadening their practical use. Finally, special attention is devoted to the future perspectives of superabsorbent core/shell composites, exploring potential innovations in material design and multifunctionality. Emerging trends such as stimuli-responsive behavior, sustainability and scalability are discussed as key factors for next-generation applications. The review also outlines challenges and opportunities that could guide future research and industrial implementation.