Facile Synthesis of Flexible Methylsilsesquioxane Aerogels with Surface Modifications for Sound- Absorbance, Fast Dye Adsorption and Oil/Water Separation

Abstract

New flexible methylsilsesquioxane (MSQ) aerogels have been facilely prepared by a sol–gel process with methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS) as co-precursors, followed by surface modification and ambient pressure drying. The microstructure, mechanical properties and hydrophobicity of these MSQ aerogels after surface modifications of hexamethyldisiloxane (HMDSO) and/or hexamethyldisilazane (HMDS) were investigated in detail, and the applications of surface-modified MSQ aerogels in sound-absorbance, fast dye adsorption and oil/water separation were evaluated, respectively. The MSQ aerogels surface-modified by HMDS possess flexibility, elasticity and superhydrophobicity, and demonstrate good performance in the mentioned applications. The resultant MSQ aerogel used in sound-absorbance has high frequency (about 6 kHz) acoustic absorptivity of up to 80%, benefiting from its macroporous structure and porosity of 94%, and it also possesses intermediate frequency acoustic absorptivity (about 1 kHz) up to 80% owing to its elasticity. This MSQ aerogel can selectively separate oil from oil/water mixtures with high efficiency due to its superhydrophobicity and superlipophilicity, resulting from a lot of methyl groups, density as low as 0.12 cm3·g−1 and a water contact angle as high as 157°. This MSQ aerogel can be assembled to be a monolithic column applied for fast dye adsorption, and shows selective adsorption for anionic dyes and removal efficiency of methyl orange of up to 95%.

Amine Modification of Silica Aerogels/Xerogels for Removal of Relevant Environmental Pollutants

“…From the examples reported above, the interaction between silica aerogels and the pollutants can be improved by modifying the aerogels’ surface chemistry. Apart from the presence of methyl groups, the presence of amino and carboxyl functional groups can also result in strong affinities towards specific contaminants [10,19,43,46]. However, some of these modifications result in the decrease of the specific surface area [10,44].…”

Fabrication and Characterization of MSQ Aerogel Coating on ePTFE Thin Films for Cable Sheaths

“…The MSQ aerogel monolith was synthesized via a sol-gel process with MTMS as the procedure, hydrochloric acid (HCl) as catalyst, water and methanol as solvents, hexadecyltrimethylammonium chloride (CTAC) as a surfactant and template, propylene oxide (PO) as a gelation agent, and 2-propanol, hexamethyldisilane/n-heptane, and heptane for multistage solvent replacement followed by ambient drying. According to the previous report [28,31], the MSQ aerogel monolith shows a unique structure in that nanoparticles form a ‘‘string-of-pearls’’-type structure owing to the introduced Si-CH 3 groups as shown in Figure 1a. The porous structure of the synthesized MSQ aerogel monolith is uniformly constructed by small spherical nanoparticles with an average diameter below 10 nm.…”

“…However, silica aerogels lack mechanical durability, which limits their application. To resolve this problem, organic–inorganic hybridization [28,29,30] using organotrialkoxysilanes, especially methyltrimethoxysilane (MTMS), as co-precursors with tetra alkoxysilane is a promising way to promote mechanical durability and flexibility. Methylsilsesquioxane (MSQ) aerogel is a kind of methyl hybrid SiO 2 aerogel monolith synthesized via a sol-gel process [28,29].…”

“…To resolve this problem, organic–inorganic hybridization [28,29,30] using organotrialkoxysilanes, especially methyltrimethoxysilane (MTMS), as co-precursors with tetra alkoxysilane is a promising way to promote mechanical durability and flexibility. Methylsilsesquioxane (MSQ) aerogel is a kind of methyl hybrid SiO 2 aerogel monolith synthesized via a sol-gel process [28,29]. Due to the methyl groups, the microstructure of MSQ aerogel tends to noncontiguous networks of bead chains rather than conventional three-dimensional space network structures [31].…”

“…Due to the methyl groups, the microstructure of MSQ aerogel tends to noncontiguous networks of bead chains rather than conventional three-dimensional space network structures [31]. This unique structure results in better flexibility, lipophilicity, and hydrophobicity [28,29]. However, for monolithic silica aerogels, the mechanical properties, such as elastic modulus and flexibility, are still not satisfactory and the fragile monolith may drop powder during transportation and application.…”