Vacuum-Dried Synthesis of Low-Density Hydrophobic Monolithic Bridged Silsesquioxane Aerogels for Oil/Water Separation: Effects of Acid Catalyst and Its Excellent Flexibility

Abstract

Low-density hydrophobic monolithic bridged silsesquioxane aerogels were prepared by vacuum drying using terephthalaldehyde (TPAL) and 3-aminopropyl-triethoxysilane (APTES) as precursors and acetic acid as catalyst. The effects of acid on the vacuum-dried synthesis of bridged silsesquioxane aerogels were investigated. The results indicate that the growth mechanism changes from cluster−cluster to monomer−cluster when acid is added, which induces the formation of the low-density monolithic aerogels with increased pore size. The methyltrimethoxysilane (MTMS) co-precursor could endow the aerogels with good hydrophobicity. The densities, pore structure, hydrophobicity, and mechanical properties of the obtained bridged silsesquioxane aerogels were investigated in detail. The results show that the monolithic aerogels possess low density (0.071 g/cm 3 ), high hydrophobicity (contact angle, >140°), and excellent flexibility (Young's modulus, 0.029 MPa). All of these characteristics make the hydrophobic aerogels competitive candidates for oil/water separation.

Recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation

“…Organic materials that are present in abundance have been considered as promising materials to enhance the bonding structure of aerogels. [ 117, 118 ] The organic nanofibers act as structural reinforcement or surface functionalizing agents in inorganic‐based scaffolds through physical or chemical cross‐linking. As reported, Si et al.…”

“…Organic materials that are present in abundance have been considered as promising materials to enhance the bonding structure of aerogels. [117,118] The organic nanofibers act as structural reinforcement or surface functionalizing agents in inorganic-based scaffolds through physical or chemical cross-linking. As reported, Si et al [119] utilized the polyacrylonitrile fibers to strengthen the network assembled by silica particles and successfully overcome the brittleness of the original structure.…”

Superwetting Polymeric Three Dimensional (3D) Porous Materials for Oil/Water Separation: A Review

“…Recently, bridged silsesquioxane aerogels are more favorable due to the significantly improved mechanical strength through the formation of covalent bonding between inorganic siloxane and organic functional groups [186]. Chen et al [187] used terephthalaldehyde (TPAL) and 3-aminopropyl-triethoxysilane (APTES) as a bridging silsesquioxane precursor and MTMS to fabricate the highly hydrophobic silicon composite aerogel (142°) via the catalytic reaction of acetic acid and freeze-drying. The bridged silsesquioxane aerogel can absorb 8–23 times oil or non-polar organic solvents of its initial weight, and are stable after more than 10 times cycling compression at 50% strain.…”

Directly ambient pressure dried robust bridged silsesquioxane and methylsiloxane aerogels: effects of precursors and solvents

“…Because of the large pore sizes, aerogels would suffer modest capillary force during the drying process, it is possible to dry the aerogels at ambient pressure with proper solvents. The aerogels can be well applied in oil absorption for their large porosity, the oil absorption capacity was measured in the same method as the previous work, 38 In the study, six common organic solvents were taken to test the absorption of the four aerogels and the result was shown in Fig. S9.…”

“…And for each aerogel, the mass gain is larger for the organic solvents with larger density, which is coincident with the results of the previous reports. 11,38 Mechanical properties…”