Hyperbranched Polycarbosiloxanes: Synthesis by Piers-Rubinsztajn Reaction and Application as Precursors to Magnetoceramics

Abstract

Silicon-containing hyperbranched polymers (Si-HBPs) have drawn much attention due to their promising applications. However, the construction of Si-HBPs, especially those containing functional aromatic units in the branched backbones by the simple and efficient Piers-Rubinsztajn (P-R) reaction, has been rarely developed. Herein, a series of novel hyperbranched polycarbosiloxanes were prepared by the P-R reactions of methyl-, or phenyl-triethoxylsilane and three Si-H containing aromatic monomers, including 1,4-bis(dimethylsilyl)benzene, 4,4 -bis(dimethylsilyl)-1,1 -biphenyl and 1,1 -bis(dimethylsilyl)ferrocene, using B(C 6 F 5 ) 3 as the catalyst for 0.5 h at room temperature. Their structures were fully characterized by Fourier transform infrared spectroscopy, 1 H NMR, 13 C NMR, and 29 Si NMR. The molecular weights were determined by gel permeation chromatography. The degrees of branching of these polymers were 0.69-0.89, which were calculated based on the quantitative 29 Si NMR spectroscopy. For applications, the ferrocene-linked Si-HBP can be used as precursors to produce functional ceramics with good magnetizability after pyrolysis at elevated temperature.

The Influence of Zinc Waste Filler on the Tribological and Mechanical Properties of Silicone-Based Composites

“…A similar tendency was also seen in samples with 10% filler (ZD10-1.3 g/cm 3 , SZA10-1.29 g/cm 3 , and ZA10-1.31 g/cm 3 ). Slightly larger differences were obtained for the samples with 20% filler (ZD20-1.48 g/cm 3 , SZA20-1.4 g/cm 3 , and ZA20-1.47 g/cm 3 ). The density of the ZD20 sample was the highest among all tested composites and was 24% higher than the density of the native silicone.…”

“…As the filler content in the composite increased, its density also increased. For samples containing 5% filler, the densities were similar (ZD5-1.22 g/cm 3 , SZA5-1.23 g/cm 3 , and ZA5-1.23 g/cm 3 ). A similar tendency was also seen in samples with 10% filler (ZD10-1.3 g/cm 3 , SZA10-1.29 g/cm 3 , and ZA10-1.31 g/cm 3 ).…”

“…For samples containing 5% filler, the densities were similar (ZD5-1.22 g/cm 3 , SZA5-1.23 g/cm 3 , and ZA5-1.23 g/cm 3 ). A similar tendency was also seen in samples with 10% filler (ZD10-1.3 g/cm 3 , SZA10-1.29 g/cm 3 , and ZA10-1.31 g/cm 3 ). Slightly larger differences were obtained for the samples with 20% filler (ZD20-1.48 g/cm 3 , SZA20-1.4 g/cm 3 , and ZA20-1.47 g/cm 3 ).…”

Catalytic Synthesis of Oligosiloxanes Mediated by an Air Stable Catalyst, (C6F5)3B(OH2)

“…Although a step-wise synthesis of oligosiloxane has been reported, it is still based on conventional condensation of silanols with chlorosilanes (Uchida et al, 1990;Matsumoto et al, 2018Matsumoto et al, , 2019. Other methods available in literature for the preparation of oligosiloxanes involve catalytic cross-coupling reactions of oxygen nucleophiles (e.g., alkoxysilanes, silanols, phenols, and ethers) with hydrosilanes (Brook, 2018;Zhang et al, 2020). The synthesis of symmetrical disiloxanes directly from hydrosilanes have been reported using InBr 3 , a reaction which involves Lewis acid-catalyzed air oxidation of hydrosilanes (Scheme 1, A, conditions I) (Sridhar et al, 2009).…”

“…Main group (and metal-free) catalysts such as B(C 6 F 5 ) 3 have gained great interest as a catalyst activator and as strong Lewis acid for many purposes (Piers, 2004;Lawson and Melen, 2017;Brook, 2018). Several studies have been published for the preparation of siloxanes and hyperbranched siloxanes involving catalytic cross-coupling reactions of oxygen nucleophiles (e.g., alkoxysilanes, silanols, phenols, and ethers) with hydrosilanes (Kawakami et al, 2004;Chojnowski et al, 2005Chojnowski et al, , 2006Chojnowski et al, , 2008Zhou and Kawakami, 2005;Shinke et al, 2007;Thompson and Davies, 2007;Cella and Rubinsztajn, 2008;Kurjata et al, 2009;Feghali and Cantat, 2014;Madsen et al, 2014;Zhang et al, 2014Zhang et al, , 2020Feghali et al, 2015;Laengert et al, 2017;Szawiola et al, 2017;Wu et al, 2017;Brook, 2018;Ai et al, 2019). Recently, Matsumoto and co-workers reported a sequencecontrolled synthesis of oligosiloxanes via dehydrocarbonative coupling of alkoxysilanes and hydrosilanes, named the Piers-Rubinsztajn reaction, and also via hydrosilylation of carbonyl compounds using B(C 6 F 5 ) 3 (Matsumoto et al, 2018).…”