Superabsorbent composites based on layered clays and mica: Synthesis, performance modulation and future challenges

Abstract

Superabsorbent materials (SAMs), three-dimensional (3D) hydrophilic polymer networks capable of absorbing and retaining hundreds of times their weight in water, demonstrate superior performance compared to conventional absorbents (e.g., cotton or cellulose sponges) in both water absorbency and retention efficiency. These exceptional properties render SAMs indispensable for critical applications ranging from personal hygiene products to precision agricultural water management. The absorption characteristics of SAMs are governed by three fundamental parameters: the chemical nature of hydrophilic functional groups, the 3D network architecture, and the cross-linking density. While the selection of monomeric units primarily determines the hydrophilic group composition—a key factor influencing production costs—contemporary research strategies emphasize performance enhancement anc cost reduction through structural modifications of the polymer network while maintaining existing monomer systems. The incorporation of nanoscale additives, particularly 2D nanoclay materials, has emerged as a transformative approach, enabling the fabrication of optimized network structures with enhanced cost-effectiveness. Among these, layered silicate clays represent an ideal class of fillers due to their natural abundance, high aspect ratio, and surface reactivity. The presence of reactive silanol (-SiOH) groups on clay surfaces facilitates the formation of robust hydrogen-bonding networks with polymer matrices, significantly improving both structural integrity and absorption performance. Various phyllosilicate minerals including montmorillonite (MMT), kaolinite, bentonite (BT), vermiculite (VMT), and rectorite (REC), have been successfully incorporated into superabsorbent composites (SACs), demonstrating their effectiveness as functional fillers. This comprehensive review systematically examines: (i) the structural design principles of clay-based SACs, (ii) their structure-property relationships, (iii) underlying absorption mechanisms, and performance optimization strategies. Furthermore, we critically discuss future research directions to fully exploit the potential of these advanced functional materials in next-generation applications.