Transparent, Highly Insulating Polyethyl- and Polyvinylsilsesquioxane Aerogels: Mechanical Improvements by Vulcanization for Ambient Pressure Drying

Abstract

Information on ExperimentsMaterials: Methanol, ethanol, 1-propanol, 2-propanol and 2-methyl-2-propanol (tert-butanol) were purchased from Kishida Chemical Co., Ltd. (Japan). 1-Butanol was purchased from Wako Pure Chemical Industries, Ltd. (Japan). All chemicals were used without further purification. Details in evaporative drying process:In order to obtain xerogels from wet gels in size of ca. 50 mm × 50 mm × 4 mm, an evaporative drying process was conducted as follows: A wet gel containing n-hexane as pore liquid was placed in a 250 mL glass jar. Then, n-hexane was added inside the jar until the top of liquid surface reached the gel surface. The opening (65 mm in diameter) of the jar was subsequently covered with a plastic wrap, the center of which was cut in ca. 1 cm square (shown in Figure S1). The glass jar was stood at room temperature until drying was completed (temporal shrinkage and reexpansion of gel occurs). No further drying at higher temperature was performed, which is conducted in a typical process for polymethylsilsesquioxane (PMSQ) xerogels. Electron microscope observation:A scanning electron microscope (SEM, JSM-6060, JEOL, Ltd., Japan) was employed in order to investigate the microstructure of aerogels. Before observation, samples were adhered onto a brass sample stage with conductive silver paste (DOTITE, Fujikura

Flexible organofunctional aerogels

“…Shimizu et al fabricated transparent polyvinylsilsesquioxane aerogels made from VTMS that show 100% resilience at 50% compression, achieved by a radical polymerization of the vinyl groups. 15 "Marshmallowlike" aerogels were produced by Hayase et al, by combining MTMS with dimethyldimethoxysilan (DMDMS) to yield aerogels and xerogels that show unusual flexibility and bendability with a reversible compression up to 80%. 16 One comment regarding the term aerogel at this point: a clear definition for an aerogel is somewhat lost with the manifold new compositions and properties.…”

Versatile Double-Cross-Linking Approach to Transparent, Machinable, Supercompressible, Highly Bendable Aerogel Thermal Superinsulators

“…As shown in Figure 2a,b and the multiple peak fitting of the NMR spectra ( Figure S1), the intense peaks located at around -64, -66, -19, and -22 ppm correspond to T 3 (CH2CH(SiO3/2))n and T 2 species 16 in the PVPSQ aerogels, T 3 (CH2CH(CH2SiO3/2))n and T 2 species 34 in the PAPSQ aerogels, D 2 (CH2CH(Si(CH3)O2/2))n and D 1 species in the PVPMS aerogels, and D 2 (CH2CH(CH2Si(CH3)O2/2))n and D 1 species in the PAPMS aerogels, respectively. 19 For PAPMS aerogels, the small peak at around -36 ppm is attributed to a small amount of silicon with unpolymerized allyl groups in CH2=CHCH2Si(CH3)O2/2.…”

“…16 The macroscopic phase separation usually results in precipitations or heterogeneous gels with low or no transparency and porosity. In the case of VMDMS and AMDMS, direct hydrolysis and polycondensation do not afford a three-dimensional network structure since it contains only two hydrolyzable groups.…”

“…Transparent polymethylsilsesquioxane (PMSQ), 14,15 polyethylsilsesquioxane (PESQ), and polyvinylsilsesquioxane (PVSQ) aerogels 16 were first obtained via this method from methyltrimethoxysilane (MTMS), ethyltrimethoxysilane (ETMS), and vinyltrimethoxysilane (VTMS), respectively. These aerogels are exceptionally strong and elastic against compression due to the lower crosslinking This is the original manuscript before revision.…”

Silicone‐Based Organic–Inorganic Hybrid Aerogels and Xerogels

“…The addition of further carbon atoms to the methyl group of MTMS offers extended possibility in designing hybrid aerogels and xerogels. In a recent paper from our group, a modified sol–gel strategy affords the porous structure with a few tens nanometers of pores in more hydrophobic polyethylsilsesquioxane (PESQ) and polyvinylsilsesquioxane (PVSQ) systems . Liquid surfactant polyoxyethylene 2‐ethylhexyl ether (EH‐208) can effectively tune the compatibility of silsesquioxane condensates and solvents, suppressing the phase separation in the course of gelation.…”