title: Transparent Ethylene-Bridged Polymethylsiloxane Aerogels and Xerogels with Improved Bending Flexibility.
abstract: Transparent, monolithic aerogels with nanosized colloidal skeletons have been obtained from a single precursor of 1,2-bis(methyldiethoxysilyl)ethane (BMDEE) by adopting a liquid surfactant and a two-step process involving strong-acid, followed by strong-base, sol-gel reactions. This precursor BMDEE forms the ethylene-bridged polymethylsiloxane (EBPMS, O2/2(CH3)Si-CH2CH2-Si(CH3)O2/2) network, in which each silicon has one methyl, two bridging oxygens, and one bridging ethylene, exhibiting an analogous structure to that of the previously reported polymethylsilsesquioxane (PMSQ, CH3SiO3/2) aerogels having one methyl and three bridging oxygen atoms. Obtained aerogels consist of fine colloidal skeletons and show high visible-light transparency and a flexible deformation behavior against compression without collapse. Similar to the PMSQ aerogels, a careful tuning of synthetic conditions can produce low-density (0.19 g cm-3) and highly transparent (76% at 550 nm, corresponding to 10 mm thick samples) xerogels via ambient pressure drying by solvent evaporation due to their high strength and resilience against compression. Moreover, EBPMS aerogels exhibit higher bending strength and bending strain at break against the three-point bending mode compared to PMSQ aerogels. This improved bendability is presumably derived from the introduced ethylene-bridging parts, suggesting the potential for realizing transparent and bendable aerogels in such polysiloxane materials with organic linking units.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Taiyo
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Kazuyoshi
authors.identifier: 0000-0001-5087-9808
authors.initials: K
authors.lastname: Kanamori
authors.affiliation: Institute for Chemical Research, Kyoto University , Gokasho, Uji-city, Kyoto 611-0011, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Maeno
authors.affiliation: Institute for Chemical Research, Kyoto University , Gokasho, Uji-city, Kyoto 611-0011, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Kaji
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Kazuki
authors.initials: K
authors.lastname: Nakanishi