Synthesis of an Organosilicon Dendrimer Containing 324 Si-H Bonds

Seyferth, Dietmar; Son, David Y.; Rheingold, Arnold L.; Ostrander, Robert L.

doi:10.1021/om00019a026

Cited by 223 publications

(135 citation statements)

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“…These groups can be exchanged with vinyl magnesium bromide to produce the first branching generation with two vinyl groups connected to each silicon atom in the SAM. 20,21 These groups can be used to initiate a living polymerization reaction to produce tethered two-arm star molecules with narrow molecular weight distributions. Alternatively, the divinyl silanes can be reacted again with dichloromethylsilane in the presence of platinum, then with vinyl magnesium bromide to produce a branched initiator with higher functionality.…”

Section: B Polymer Dynamics Near Surfacesmentioning

confidence: 99%

Tethered Lubricants for Small Systems

Archer¹

2006

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The objective of this research project is two-fold. First, to fundamentally understand friction and relaxation dynamics of polymer chains near surfaces; and second, to develop novel self-lubricated substrates suitable for MEMS devices. During the last three years of the study the PI and his students have executed all tasks promised in the grant proposal. Details of research accomplishments in each area of the project are described in the next sections. Research A. Interfacial Friction and Dynamics of Alkylsilane SAMsThe main hypothesis that guides our work is that molecular-scale disorder in monolayer films tethered to substrates enhances molecular freedom and improves lubrication and ware properties of thin films. Self-assembled monolayers (SAMs) are in most cases the first choice for creating self-lubricated substrates for small systems (e.g. MEMS and NEMS). SAMs are attractive as lubricating coatings for a variety of reasons.1-3 If the SAMs are created using low surface energy molecules (e.g. alkane or fluorinated alkanes), for example, they reduce interfacial adhesion between substrates to which they are attached, which reduces the interfacial friction coefficient. SAMs can also reduce adhesion by preventing adsorption of stiction promoting species such as water to the substrate. Furthermore, because molecules comprising the SAM are chemically bonded to the substrate, a well-designed SAM coating can retain its lubricating properties through multiple cycles of interfacial shear. The thickness of most SAM coatings is rarely greater than a few nanometers, making these systems ideal for lubricating small mechanical systems such as in MEMs and NEMs. Boundary lubrication properties of several SAM systems, including alkanethiols (CH 3 (CH 2 ) n-1 SH) on Au, Ag, and Cu, and alkyltrichlorosilanes (CH 3 (CH 2 ) n-1 SiCl 3 ) on SiO 2 and mica, have been studied primarily by experiment to establish connections between SAM order, chemistry, and lubrication properties. A important finding is that SAMs formed by long alkylsilane or alkenethiol molecules (chain length >10) provide the best lubrication.2,4 It has been asserted in the literature, without proof, that greater disorder within SAMs comprised of shorter molecules (chain length <10) yields more energy dissipation modes, which increases interfacial friction. 3,5 This assertion contradicts the notion that molecular-scale disorder in monolayer films enhances dynamics and improves lubrication properties.Zhang and Archer recently used Lateral force Atomic Force Microscopy, dynamic contact angle measurements, infrared spectroscopy, and theory to study the interfacial properties of alkyl silane SAMs with varying amounts of disorder.6 Disorder was introduced in the SAMs by mixing two self-assembling components with different molecular weights in varying amounts. Mixed twocomponent (C n /C 18 ) alkylsilane SAMs formed in this manner were confirmed to possess greater levels of orientation disorder using infrared spectroscopy and hexadecane contact angle measurements. 6 Signi...

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Section: B Polymer Dynamics Near Surfacesmentioning

confidence: 99%

Tethered Lubricants for Small Systems

Archer¹

2006

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“…The divergent synthetic route starts with 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) as a tetrafunctional core (generation 0) and approximates to the valuable methodology that has been previously used by van der Made et al, 34 Zhou and Roovers, 35 Seyferth et al 36 and by our own group 6,21 for the synthesis of carbosilane dendrimers, and involves the repetition of hydrosilylation and alkenylation reactions as the growing steps.…”

Section: Synthesis and Characterization Of Cyclotetrasiloxane-based Dmentioning

confidence: 99%

Cyclic siloxanes and silsesquioxanes as cores and frameworks for the construction of ferrocenyl dendrimers and polymers

Casado

Cuadrado

Morán

et al. 1999

Appl. Organometal. Chem.

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Starting from 1,3,5,7‐tetramethylcyclotetrasiloxane as core, novel ferrocenyl silicon‐containing dendrimers have been constructed up to the third generation, which contains 16 peripheral ferrocene moieties. As precursors of these ferrocenyl dendritic molecules, SiCl‐ and Siallyl‐terminated cyclotetrasiloxane‐based dendrimers were also built step by step, by the repetition of hydrosilylation and alkenylation reactions as growing steps. The dendritic structures have been confirmed by 1H, 13C and 29Si NMR, infrared spectroscopy, elemental analysis, mass spectrometry and vapor‐pressure osmometry. Solution electrochemical studies showed that all the ferrocenyl redox centers attached to the dendritic surface behave as independent, electronically isolated units, so that the dendrimers exchange all the electrons simultaneously at the same potential. We also describe the application of the first redox‐active ferrocenyl polymer containing an octakis(dimethylsiloxy)octasilsesquioxane framework, as a mediator in the electrocatalytic oxidation of ascorbic acid. Copyright © 1999 John Wiley & Sons, Ltd.

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“…More recently, examples of dendrimers with silicon-included, such as carbosilane and siloxane, that have come to the fore. [7][8] The dendrimers including silicon can be classified into three main categories, having siloxane (Si-O), 9 carbosilane (Si-C) [10][11][12][13][14][15] or polysilane (Si-Si) 16 backbones. Synthetic methods for the preparation of silicon-containing dendrimers were reported by many researchers who used the simple repeating procedures such as hydrosilylation, dehydrocoupling, alkenylation as well as alcoholysis.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of novel bis[(tris(dimethylsilyl)methyl)alkyl]ferrocene derivatives as new ferrocenyl multi-functional silyl ether compounds

Teimuri‐Mofrad¹,

Abbasi²,

Safa³

et al. 2016

Arkivoc

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Some new branched polysilyl ethers with a ferrocene core were synthesized through treatment of 1,1´-bis[tris(dimethylsilyl)methyl]alkylferrocenes with various alcohols by Karstedt catalyst. Bis(chloroalkyl)ferrocenes are synthesized by acylation of ferrocene with 3-chloropropanoyl chloride and 4-chlorobutanoyl chloride. The obtained 1,1´-bis(3-chloropropanoyl)ferrocene and 1,1´-bis(4-chlorobutanoyl)ferrocene underwent a reduction and chlorides were replaced by bromides, and then they were treated with (Me3Si)3CLi and (HMe2Si)3CLi give silane compounds 6a-b and 7a-b.

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Synthesis of an Organosilicon Dendrimer Containing 324 Si-H Bonds

Cited by 223 publications

References 0 publications

Tethered Lubricants for Small Systems

Tethered Lubricants for Small Systems

Cyclic siloxanes and silsesquioxanes as cores and frameworks for the construction of ferrocenyl dendrimers and polymers

Synthesis of novel bis[(tris(dimethylsilyl)methyl)alkyl]ferrocene derivatives as new ferrocenyl multi-functional silyl ether compounds

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