Fabrication of organic-inorganic double-walled (ER@EC/SiO2) microcapsules via biomimetic mineralization for self-healing cementitious materials

Abstract

The performance of self-healing cementitious materials can be enhanced by improving the interfacial transition zone (ITZ) between microcapsules and cementitious materials. Silicon dioxide (SiO₂), which serves as the outer wall material of microcapsules, can enhance the ITZ performance and strengthen the cementitious material matrix. In this study, organic-inorganic double-walled microcapsules were synthesized through the biomimetic mineralization method. The core material consisted of epoxy resin (ER), while the inner wall was made of ethyl cellulose (EC). The outer wall was composed of SiO₂. The morphology, ζ-potential value, chemical structure, thermal stability, mechanical properties, triggering properties, and self-healing capabilities were characterized. The effect of biomimetic mineralization was confirmed. The results showed that the microcapsules exhibited a regular spherical shape with a rough surface and a distinct inorganic wall structure. The macromolecule inducer polyethyleneimine (PEI) and anionic ethyl cellulose formed a macromolecule-anion complex. The microcapsules showcased triggering properties in simulated pore solutions of cementitious material. Montmorillonite-modified double-walled microcapsules with SiO₂ as the outer wall (MDMSiO₂) exhibited remarkable self-healing performance, achieving a maximum recovery rate of 94.1 %. The addition of MDMSiO₂ to cementitious materials resulted in a significant increase in material strength (31.58 %) after three days. The synergistic effect of biomimetic mineralization and first-principles calculations suggested that this approach can effectively guide the deposition of inorganic substances and reduce their reaction energy barriers, underscoring the potential to enhance the performance of cementitious materials.