Preparation of Polyaryloxysilanes and Polyaryloxysiloxanes by B(C₆F₅)₃ Catalyzed Polyetherification of Dihydrosilanes and Bis-Phenols

Abstract

Polyaryloxysilanes and siloxanes (PAS) are an interesting and useful class of polymers with excellent flammability characteristics. The B(C 6 F 5 ) 3 catalyzed dehydrocondensation of bis-phenols or their simple alkylethers with dihydrosilanes and siloxanes provides ready access to these polymers. The reaction proceeds readily even when hindered phenol or silane substrates are employed affording sterically protected PAS derivatives. The combination of steric hindrance around the silyl ether linkage, the absence of ionic impurities and the use of very low levels of the boron catalyst in these reactions produces thermally and hydrolytically robust materials, which should further enhance their utility. Phenol functional macromonomers, such as polycarbonate and PPO derivatives, are readily coupled, providing easy access to siloxane copolymers. The only severe limitation of this process for preparing PAS derivatives is that the reaction is intolerant of base functionality in either the monomers or solvents used in the reactions.

Dehydrocoupling routes to element–element bonds catalysed by main group compounds

“…Since the lone pairs on the alcohol (or other functional groups present) may interact with the catalyst, dissociation of the alcohol from the [R(H)O-B(C 6 F 5 ) 3 ] adduct to regenerate free B(C 6 F 5 ) 3 is necessary before it can interact with the silane. 41 The dehydrocoupling of phenols with the silane Et 3 SiH using a phosphonium catalyst [(C 6 F 5 ) 3 PF][B(C 6 F 5 ) 4 ] 42 (Scheme 17) has also been studied (see ESI, † Fig. 38 These mechanisms have been found to be similar to those observed for transition metal catalysed Si-O bond forming dehydrocoupling reactions in that Si-H bond activation occurs in the initial step of the reaction.…”

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

“…[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 ). [55] Table 2. [39] Significant scrambling of the siloxane backbone arises from exchanging hydrogen and alkoxy groups attached to silicon atoms.…”

Facile Synthesis of Cx(AB)yCx Triblock Silicone Copolymers Utilizing Moisture Mediated Living‐End Chain Extension

“…Functional silicone precursors bearing SiH and SiOR groups can be sourced from silicone polymers (pendant or telechelic functionality) or from small silanes . In addition to alkoxysilanes, analogous reactions occur with silanols (including mineral surfaces), borates, phenols, and alkyl aryl ethers (Figure B) . Recently, the use of water as a chain extender for α,ω‐hydride‐terminated poly(dimethyl)siloxanes (H‐PDMS‐H) was described.…”