Synthesis and characterization of well-defined poly(methyl methacrylate)/CaCO3/SiO2 three-component composite particles via reverse atom transfer radical polymerization

Calcium carbonate: controlled synthesis, surface functionalization, and nanostructured materials

Calcium carbonate (CaCO₃) is an important inorganic mineral in biological and geological systems. Traditionally, it is widely used in plastics, papermaking, ink, building materials, textiles, cosmetics, and food. Over the last decade, there has been rapid development in the controlled synthesis and surface modification of CaCO₃, the stabilization of amorphous CaCO₃ (ACC), and CaCO₃-based nanostructured materials. In this review, the controlled synthesis of CaCO₃ is first examined, including Ca²⁺-CO₃^2- systems, solid-liquid-gas carbonation, water-in-oil reverse emulsions, and biomineralization. Advancing insights into the nucleation and crystallization of CaCO₃ have led to the development of efficient routes towards the controlled synthesis of CaCO₃ with specific sizes, morphologies, and polymorphs. Recently-developed surface modification methods of CaCO₃ include organic and inorganic modifications, as well as intensified surface reactions. The resultant CaCO₃ can then be further engineered via template-induced biomineralization and layer-by-layer assembly into porous, hollow, or core-shell organic-inorganic nanocomposites. The introduction of CaCO₃ into nanostructured materials has led to a significant improvement in the mechanical, optical, magnetic, and catalytic properties of such materials, with the resultant CaCO₃-based nanostructured materials showing great potential for use in biomaterials and biomedicine, environmental remediation, and energy production and storage. The influences that the preparation conditions and additives have on ACC preparation and stabilization are also discussed. Studies indicate that ACC can be used to construct environmentally-friendly hybrid films, supramolecular hydrogels, and drug vehicles. Finally, the existing challenges and future directions of the controlled synthesis and functionalization of CaCO₃ and its expanding applications are highlighted.

Silanized Silica-Encapsulated Calcium Carbonate@Natural Rubber Composites Prepared by One-Pot Reaction

This article demonstrates the one-pot reaction, an efficient and environmentally friendly organic synthesis method, utilized to prepare the silanized silica-encapsulated calcium carbonate@natural rubber composites (SSC@NR), following first mixing the calcium carbonate (CaCO₃) solution, silica (SiO₂) sol solution and a small amount of Si-69 solution, to modify the surface of CaCO₃ particles, and then wet mixing with natural rubber latex. The obtained silanized silica-encapsulated calcium carbonate (SSC) particles were tested by TGA, FTIR and XRD, to substantiate the effect of surface modification. Moreover, the effects of the amount of SSC on the Mooney viscosity, curing characteristics, physical and mechanical properties and dynamic mechanical properties of the SSC@NR were investigated. The results show that the surface of modified CaCO₃ is effectively coated with SiO₂ particles by means of physical and chemical combination, to achieve the effect of surface coating. When the optimum amount of SSC filler is 40 phr, the SSC can form better physical adsorption and chemical combination with the NR molecular chains and can be evenly dispersed in the rubber matrix, resulting in the conspicuous improvement of physical and mechanical properties, such as the tensile strength, tear strength, elongation at break and abrasion resistance. Meanwhile, the compound with SSC has preferable processability and dynamic mechanical properties.