Silica−Dimethylsiloxane HybridsNon-Hydrolytic Sol−Gel Synthesis and Characterization by NMR Spectroscopy

Abstract

The non-hydrolytic sol-gel process provides a facile route to silica-dimethylsiloxane (DMS) hybrids starting from silicon(IV) chloride, tetraethoxysilane (TEOS), and hexamethylcyclotrisiloxane, D 3 . Both the non-hydrolytic sol-gel silica synthesis and ring-opening polymerization of the D 3 are initiated simultaneously by the presence of an iron(III) chloride catalyst. Evidence for the structures of these hybrids is presented from the results of solid-state 2D NMR correlation spectroscopy. The siloxane component consists of short D units, which show good compatibility with the silica on a molecular level, probably as a result of copolymerization between Q and D units.

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

“…The synthesis of 3D cross-linked polysiloxanes has been described by Vioux and coworkers [78,112], and Hay and Raval [113][114][115]. Redistribution reactions of alkoxy and chloro groups take place readily at r.t., while the condensation reactions occur at temperatures from 35 to 150 • C and were catalyzed by Lewis acidic metal chlorides, similar to the syntheses of metal oxides (Section 2.1).…”

Siloxane‐Bond Formation Promoted by Lewis Acids: A Nonhydrolytic Sol–Gel Process and the Piers–Rubinsztajn Reaction

“…Although condensation proceeds to form siloxane bonds, group-exchange reactions compete to form randomly co-condensed siloxanes. [53] The Piers-Rubinsztajn reaction provides alternating copolymers by the heterofunctional condensation between Ph 2 Si-(OMe) 2 and 1,1,3,3-tetramethyldisiloxane ( H MM H ). [52] The formation of cyclosiloxane besides PDMS is frequently observed in hydrolysis-condensation processes.…”

“…Cyclosiloxanes can be a siloxane source in NHSG. [53] The Piers-Rubinsztajn reaction provides alternating copolymers by the heterofunctional condensation between Ph 2 Si-(OMe) 2 and 1,1,3,3-tetramethyldisiloxane ( H MM H ). Small amounts of cyclosiloxanes also form as by-product (Scheme 3).…”

Óxido misto de ítrio-alumínio dopado com Eu(III)

“…O processo sol-gel não-hidrolítico recentemente desenvolvido tem sido empregado como metodologia alternativa, devido à sua versatilidade como método de preparação de óxidos inorgânicos 3 . A rota solgel não-hidrolítica envolve a reação de um haleto metálico com um doador de oxigênio, tal como álcool ou éter, para formar um alcóxido na ausência de umidade, com posterior formação do óxido inorgânico 4 .…”

“…A literatura sobre essa metodologia tem aumentado nos últimos anos. O processo tem sido usado para a obtenção de óxido de alumínio e silício contendo diferentes tipos de compostos 3,[5][6][7][8][9] .…”