Tris(pentafluorophenyl)borane as a Superior Catalyst in the Synthesis of Optically Active SiO-Containing Polymers

Deng

et al. 2006

Chemistry A European J

A template synthesis of the soluble, high molecular weight (Mw), and perfect p-phenylenediimino (p-PDA)-bridged ladderlike polyphenylsiloxane (PLPS) is reported. First, N,N'-bis(phenyldichlorosilyl)-p-PDA monomers were self-assembled into a perfect ladder superstructure (LS) by concerted interaction of aromatic pi-pi stacking and hydrogen bonding. Then the LS underwent a novel stoichiometric hydrolysis/dehydrochlorination-condensation reaction instead of the usual hydrolysis/dehydration-condensation reaction, leading to the PLPS. The perfect ladder structures of both the PLPS and, in particular, the unstable supramolecular LS were confirmed as follows. 1) There are two Bragg peaks in solid and/or solution X-ray diffraction (XRD) spectra representing the ladder width (w) and ladder thickness (t); these peaks were consistent with those calculated by molecular simulation. 2) Both the PLPS and LS have extremely sharp absorption peaks with small half-peak widths (Delta(1/2) < 0.3 ppm) in 29Si NMR spectra, suggesting the presence of the perfect ladder structure for PLPS and LS. 3) Moreover, no noticeable absorption peaks for the Si-OH and NH2 groups were observed in FT-IR and 29Si NMR spectra, indicating that the Si-N bond of the [triple bond]Si-NH-C6H4-NH-Si[triple bond] ladder rung of PLPS and LS is not cleaved. 4) Both PLPS and LS show similar emission peaks (in fluorescence spectroscopy) attributed to the excimer formed by face-to face pi-pi stacking of phenyl groups along the ladder chain rather than a branched direction. 5) Differential scanning calorimetry (DSC) measurements indicate a high glass temperature (Tg = 176.4 degrees C) for PLPS. As circumstantial evidence, this result further indicates very high stiffness of PLPSs ladder backbone as compared with flexible single-chain polyphenylmethylsiloxane with a low Tg = -69.4 degrees C.

mentioning

confidence: 99%

Supramolecular Template‐Directed Synthesis of Perfect Phenelenediimino‐Bridged Ladderlike Polyphenylsiloxanes

Deng

et al. 2006

Chemistry A European J

Macro Chemistry & Physics

“…With aryl methyl ethers as the nucleophile, it was necessary, if undesirable, to include toluene in the reactions to solvate the aryl ether. For related alternating copolymer reactions that use alkoxysilane monomers that are more soluble in silicones, this solvent may not be necessary …”

Section: Discussionmentioning

confidence: 99%

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

Schneider

Laidley

Brook

2019

The physical and chemical properties of silicone block copolymers depend upon the block size and chemical characteristics. Silicone block copolymer synthetic procedures typically involve chain‐growth polymerization techniques that are difficult to control, require low temperatures, inert atmospheres, etc., and which are subject to polymer chain redistribution; the latter process broadens dispersity and leads to the formation of cyclic monomers that must be removed. Once formed, tuning the size of the individual blocks is challenging. The controlled one‐pot synthesis of organosilicone Cx (AB)y Cx triblock copolymers with aryl rich cores is demonstrated by exploiting the Piers–Rubinsztajn reaction and a hydrolysis/condensation polymerization, both using B(C6F5)3 catalysis. A fast Piers–Rubinsztajn reaction between HSi‐terminated silicones and aryl phenyl ethers leads preferentially to the formation of the aryl‐rich core. Subsequent addition of HSi‐terminated silicones permits controlled chain extension of the flanking homosilicone blocks via a slower hydrolysis/condensation facilitated by atmospheric moisture and leads in one pot, two steps to clean Cx (AB)y Cx triblocks. The products are surprisingly resilient to hydrolysis.

“…By Tris(pentafuluorophenyl)borane 20 To the mixture of 1OH (0.42 g, 0.30 mmol) or 1OMe (0.44 g, 0.30 mmol) and 4H (0.30 mmol) in dry toluene (5 mL), B(C 6 F 5 ) 3 (0.002 g, 3.00 mmol) was added as the catalyst. After reacting at room temperature for 5 h, the polymer was precipitated into methanol.…”

Section: Polymerizationmentioning

confidence: 99%

Precise Synthesis of Poly(silphenylenesiloxane)s with Epoxy Side Functional Groups by Tris(pentafluorophenyl)borane as a Catalyst

Xue

Kawakami

2007

Polym J

Self Cite

ABSTRACT:1,!-Dimethylhydroxysilyl, -dimethylhydrosilyl, -dimethylmethoxysilyl -terminated tetramethylsilphenylenesiloxane prepolymers were prepared by sequential palladium-catalyzed dehydrocoupling polymerization of 1,4-bis(dimethylsilyl)benzene with water, reduction with lithium aluminium hydride, and palladium-catalyzed methanolysis. 1,4-Bis[(glycidyl-or cyclohexene oxide-functionalized alkyl)methylhydrosilyl]benzene and methyldimethoxysilanes with the same epoxy groups were synthesized by hydrosilylation of 1,4-bis(methyldihydrosilyl)benzene and methyldimethoxysilane with (terminal olefin-functionalized alkyl) substituted epoxides in the presence of platinum catalyst. 1,4-Bis[(glycidyl-or cyclohexene oxide-functionalized alkyl)methyl(hydroxy or methoxy)silyl]benzenes were obtained by hydrolysis and methanolysis of the hydrosilyl derivatives. Poly(silphenylenesiloxane)s with epoxy side groups were synthesized by hetero-polycondensation of the hydrosilane, hydroxysilane and methoxysilane functional groups in the prepolymer and 1,4-bis[(epoxy-functionalized alkyl)methylsilyl]benzene, or 1,1-dimethoxy(epoxy-functionalized alkyl)methylsilane in the presence of a catalyst. Tris(pentafluorophenyl)borane was found to be an excellent catalyst for the polymerization. Cross-linking a polymer with 1,4-diaminobenzene gave stretchable polymer film by solution cast method. Modern technologies have continuous demands on development of high-temperature elastomeric materials. Polysiloxanes are a kind of good candidates as high-temperature elastomer because of the property originated from flexible and heat-resistant Si-O-Si backbone, which is also the origin of good dielectric and surface properties, and so on. 1-3However, some thermal degradation reaction of polysiloxanes was noticed at high temperature. Corriu 4 elucidated that the main course of degradation of polysiloxane is the intermolecular exchanges of Si-O bonds, followed by intramolecular exchanges of Si-O bonds to depolymerize. Incorporation of rigid aromatic units into the siloxane backbone generally interrupts the siloxane redistribution reaction at high temperature, and improves both mechanical and thermal properties without simultaneous loss of other good features of polysiloxanes. Thus, polysilarylenesiloxanes, derivatives of polysiloxanes by partially replacing -O-by arylene groups, show better thermal and mechanical property than polysiloxanes. 2,3,5,6 Polysilphenylenesiloxanes, a class of typical polysilarylenesiloxane, were intensively reported as materials possessing thermal stability and satisfying low temperature elasticity, although their crystallinity is usually higher than polysiloxanes, which is a possible obstacle in various applications, for instance, application in electronic device materials as a thin film. One of the attractive aspects of these polymers is the easiness of introducing variety of functional substituents, such as vinyl, phenyl, hydrido, flouroalkyl, etc. 7-11These functional groups were found to significantly affect the thermal p...