Exhaustive and partial alkoxylation of polymethylhydrosiloxane by copper‐catalyzed dehydrocoupling with alcohols: Synthesis, crosslinking behavior, and thermal properties of the products

Abstract

Polymethylhydrosiloxane (PMHS) reacts with aliphatic and aromatic alcohols at room temperature in the presence of [CuH(PPh 3 )] 6 complex catalyst to give poly[(methyl) (alkoxy)siloxane]s in high yields. Reactivity of alcohols decreases in the order of p-methoxyphenol > p-cresol > phenol > benzyl alcohol > allyl alcohol > ethanol > isopropanol > tert-butyl alcohol. Partially p-cresylated polymers, which still retain unreacted SiAH bonds, react further with ethylene glycol or water to form cross-linked polymers, which, depending on the extent of cross linking, gelate during the cross-linking process. Propargyl alcohol reacts with PMHS very rapidly to give exhaustively and partially propargyloxylated PMHS. Resulting polymers, upon heating, undergo crosslinking. Partially propargyloxylated polymers display high thermal stability [T d5 (temperature of 5% weight loss) > 500 C] as compared with starting PMHS (243 C) and exhaustively propargyloxylated one (414 C).Additional Supporting Information can be viewed in the online issue of this article.

Co2(CO)8 as an efficient catalyst for the synthesis of functionalized polymethylhydrosiloxane oils and unconventional cross-linked materials

“…2 To the best of our knowledge, the current types of functionalization of polysiloxane Si-H bonds are limited to the formation of new Si-O-R (R=alkyl, aryl, acyl) and Si-R (R=alkyl) bonds (Scheme 1) in polysiloxane oils. For example, Cu 7 and Zn 8 based catalysts, and tris(pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) 9 are known to catalyze the synthesis of functionalized PMHS (polymethylhydrosiloxane) via dehydrogenative coupling using alcohols or carboxylic acids (Scheme 1a). However, when the formation of new Si-C bond is preferred, there is only one example in the literature where a non-precious metal Ni complex was successfully used to functionalize PMHS with 1hexene or 1-octene (Scheme 1a).…”

A novel crosslinking agent of polymethyl(ketoxime)siloxane for room temperature vulcanized silicone rubbers: synthesis, properties and thermal stability

“…by the elimination of hydrogen molecules. To this date, most of researchers are mainly focused on the dehydrocoupling between alcohol and hydrosilane (or hydrosiloxane), 39,40 and the reaction between other active hydrogen (like NH 2 , HS and C]N-OH) and Si-H is seldom investigated. Hence, we prepare a novel crosslinker PMKS by dehydrogenation between acetoxime and PMHS to vulcanize silicone rubber at 25 C.…”

Kinetics of catalyzed dehydrocondensation of hydrogen functionalized siloxane

“…29,30 These experiments have been mostly conducted in dry toluene, 19,21,22 or benzene. 29,31 On the alcoholysis of PMHS, Safa et al implemented the Speier's and Karstedt's catalysts in xylene, which were found to be applicable for primary and secondary alcohols. 18 The most recent study, by Jur askov a et al monitored the ethanolysis of PMHS (7%-9%, 15%-18%, and 45-55% H-functionalized) among other hydrosiloxanes which are widely known in the silicone industry.…”

“…Namely, potassium hydroxide, 21–25 hexachloroplatinic acid, 23,25,26 Speier's or Karstedt's catalyst, 18,19 Pt/C, 21 palladium nanoparticles and rhodium complex, 27,28 also copper and tetrabutylammonium fluoride catalysts have been considered 29,30 . These experiments have been mostly conducted in dry toluene, 19,21,22 or benzene 29,31 …”

“…Namely, potassium hydroxide, [21][22][23][24][25] hexachloroplatinic acid, 23,25,26 Speier's or Karstedt's catalyst, 18,19 Pt/C, 21 palladium nanoparticles and rhodium complex, 27,28 also copper and tetrabutylammonium fluoride catalysts have been considered. 29,30 These experiments have been mostly conducted in dry toluene, 19,21,22 or benzene. 29,31 On the alcoholysis of PMHS, Safa et al implemented the Speier's and Karstedt's catalysts in xylene, which were found to be applicable for primary and secondary alcohols.…”