Fabrication of Densely Spaced Hollow Silica Spheres with Controlled Sizes Using Block Polymers for Applications as Aerogels

Abstract

The nanoscale hollow porous structure exhibits thermal conductivity similar to silica aerogel due to its lower density and high closed cavity structure. However, the traditional preparation methods of such structures face major challenges in achieving accurate morphological control under high-concentration synthesis conditions. In this study, a series of multiblock copolymers were synthesized, which can form a stable water/oil/water vesicle system with the oil phase over a wide concentration range and can be used as a template to synthesize mesoporous silica hollow spheres at ultrahigh precursor concentrations. By controlling the ethanol content in the reaction formation process, we can control the size, stacking mode, and adhesion degree of silica hollow spheres and finally prepare controllable particle size nonadhesion silica hollow spheres and aerogels with different stacking morphology, particle size, and adhesion degree of silica hollow spheres as structural elements. Due to their hollow and porous structural units and the three-dimensional network skeleton structure similar to conventional aerogels, our aerogels exhibit extremely low thermal conductivity (37.8 mw k^–1 m^–1) and density (0.056 g cm^–3), while the large skeleton size allows our aerogel to have extremely high structural strength (Young’s modulus of 117.9 MPa) and can be dried directly under atmospheric pressure. In addition, we also explored the reasons for the formation of hollow structures and what kind of block structures can be used to construct hollow structures, which will provide theoretical directions for the synthesis of hollow structures by soft templates.