Block Lightweight Superhydrophobic Geopolymer Based on Double-Silanes Synergistic Effect

Lightweight geopolymers often face application limitations due to their porosity and hydrophilicity. In this study, lightweight geopolymers with overall superhydrophobicity were successfully developed by optimizing the pore structure through a synergistic approach. This process involved combining hexadecyltrimethoxysilane (HDTMS) and poly(methylhydrosiloxane) (PMHS) in a one-step synthesis. The chemical compositions and microstructures were analyzed using techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). The effects of varying siloxane chain lengths and their additions on cofoaming were also discussed. Results indicated that HDTMS siloxanes significantly enhanced the homogeneity of pore distribution, leading to smaller average pore sizes (∼180 μm). The resulting BLS-Geopolymers (block lightweight superhydrophobic geopolymers) maintained superhydrophobicity even after mechanical grinding and polishing, demonstrating superior stability, a 3-fold improvement in thermal insulation, and a delayed freezing time from 986 to 7237 s. This study provides an effective optimization strategy to enhance the durability of lightweight geopolymers and serves as a crucial reference for the design and application of bulk porous superhydrophobic materials.