Chain transfer processes in dichlorosilane reductive polymerization and their control: A simplified route to high molecular weight polysilylenes

Zeigler, John M.; McLaughlin, L.I.; Perry, Robert J.

doi:10.1007/bf00683515

Cited by 17 publications

(13 citation statements)

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“…The results shown for both toluene and benzene solvents (entries 6 and 7) are comparable. This is surprising in light of the report of Zeigler et al 19 who find that for NaK of similar composition, the use of toluene solvent greatly reduces the polymer molecular weight in the polymerization of PhMeSiC1 2 relative to that observed in benzene. Perhaps the fact that these authors apparently conducted their polymerizations at solvent reflux is responsible for this difference.…”

Section: Discussionmentioning

confidence: 85%

“…If so, the polymerization temperature is truly a very important variable in the heterogenous Wurtz-type polymerization process. Another possible source of this discrepancy is the nature of the sodium dispersion itself, since Zeigler et al 19 apparently used commercial dispersion while ours was freshly prepared. We have also surveyed a number of aromatic solvents in the polymerization of DCEPS at 65°C.…”

Section: Discussionmentioning

confidence: 94%

“…1 7 With vigorous stirring, ultrasonic activation is not necessary, and the polymerizations go to completion, even though the sodium is not liquid under the reaction conditions. Recently, Zeigler et al 19 have reported similar resulrs using liquid NaK alloy. The preparation of some polysilanes in good yield using sodium sand in diethyl ether employing a crown ether additive has also been 808 reported by Jones et al 18 The utility of the low temperature procedures, particularly for large scale runs, stimulated us to study the process in more detail.…”

mentioning

confidence: 75%

“…As noted earlier, solvent changes (benzene, p-t-butylbenzene, toluene) also have relatively little effect on the course of the polymerization ofDCEPS. Toluene is, in principle, a hydrogen atom donating solvent, and the low polymer molecular weight of PMPS in toluene using NaK has been ascribed to hydrogen atom abstraction from solvent, 19 although the calculated bond energies suggest that benzylic hydrogen abstraction by a polycatenated silyl radical would probably be endothermic. Even so, the measured rate constant (300 K) for reaction of triethylsilyl radicals with toluene is substantial ( 1.2 x l 0 6 l mol -1 s -1 ).…”

Section: Discussionmentioning

confidence: 99%

“…These techniques often employ reaction temperatures below the melting point of sodium 16 -18 or use liquid sodium-potassium alloys. 19 The first description of a low temperature Wurtz-type polymerization procedure for the preparation of aryl polysilanes was by Matyjaszewski and co-workers, who showed that high molecular weight poly(methylphenylsilane( (PMPS) could be prepared at room temperature using strong ultrasonic activation. 16 Although this technique may yield essentially monomodal PMPS, there are also certain drawbacks.…”

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confidence: 99%

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Low Temperature Wurtz-Type Polymerization of Substituted Dichlorosilanes

Miller

Ginsburg

Thompson

1993

Polym J

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ABSTRACT:We have studied the heterogeneous Wurtz-type polymerization of a number of substituted dichlorosilanes at low temperatures as a function of solvent, metal reductant, reaction temperature, reagent stoichiometry, and additives. At 65°C, aryl dichlorosilanes rapidly produce polymer while dialkyl substituted monomers do not in the absence of additives. While the rate of polymerization of the former is relatively insensitive to steric effects, it is greatly reduced by the presence of electron donating substituents. Reaction temperature is an important variable with higher temperatures producing lower yields of multimodal products. At 65°C substituted dichlorosilanes produce high molecular weight products at low monomer conversions independent of reagent stoichiometry in a manner more consistent with a chain growth process. Polymerization in the presence of potential hydrogen donating solvents and additives produced no evidence for hydrogen atom chain transfer which would be expected if trappable silyl radicals are intermediates. The evidence is more consistent with silyl anions rather than silyl radicals as the propagating species in the heterogeneous polymerization.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 94%

mentioning

confidence: 75%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Low Temperature Wurtz-Type Polymerization of Substituted Dichlorosilanes

Miller

Ginsburg

Thompson

1993

Polym J

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Inorganic High Polymers

Roy

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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Since the development and commercialization of the polysiloxanes, a number of linear, inorganic‐backbone polymers have been reported. Most prominent among these are the polyphosphazenes and the polysilanes. Some, like poly(sulfur nitride) and the polycarborane–siloxanes, have manufacturing or stability problems. The heterophosphazenes, the alkyl/arylphosphazenes, and the polyoxothiazenes are relatively new and awaiting development and breakthrough in manufacturing technology for a number of potential applications. The polyphosphazenes with PO and PN‐bonded substituents (synthesized by a ring‐opening polymerization–substitution route) are the most mature and have seen limited manufacturing and commercialization in the area of specialized rubber markets. These polymers are extremely versatile in terms of potential applications in the areas of biomedical technology, elastomers, solid‐state batteries (via ionic conduction), catalysis, etc. The poly(alkyl/arylphosphazenes), synthesized by a polycondensation route, possess many of the properties of the PO‐ and PN‐substituted polymers and appear to be suitable for application as wide temperature‐range elastomers, thermoplastic polymers, and biomaterials. The polysilanes, which can be prepared by a number of methods are a unique class of polymers in exhibiting σ‐conjugation along the backbone. The majority of the developing applications for these polymers are based on this phenomenon, which leads to near‐uv photoabsorption, thermo‐ and piezochromism, and photodegradation. For many of the existing and developing inorganic‐backbone polymers with potential for commercial applications, a pivotal aspect for manufacture is relative ease of industrial scale‐up. This translates into readily accessible and relatively inexpensive starting materials, in addition to a process that allows flexibility with equipment and is environmentally friendly.

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Inorganic High Polymers

Roy

2009

Kirk-Othmer Encyclopedia of Chemical Technology

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Inorganic polymers embrace a very large number of elements and compounds that are constructed of units bonded together in some type of repetitive fashion with the requirement that the element carbon be excluded from the backbone of these repeating units. Some of the most common examples are the metals, as well as naturally occurring silicate minerals and silica. This article covers linear, mainly covalent macromolecules where the skeletal repeat unit is composed of primarily noncarbon elements. Inorganic polymer development has not kept pace with organic polymer development. However, preparation of inorganic polymers produce materials whose special properties are unlikely to be obtained from carbon‐based polymers. Polyphosphazenes and polysilanes have been studied extensively and are discussed here. Discussions of polyalkyl/aryloxothiazenes, polygermanes, and polystannes are included. Some applications include in the following fields: biomedical, optical materials, elastomers, flame retardants, photoinitiation, and light emitting materials.

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Chain transfer processes in dichlorosilane reductive polymerization and their control: A simplified route to high molecular weight polysilylenes

Cited by 17 publications

References 2 publications

Low Temperature Wurtz-Type Polymerization of Substituted Dichlorosilanes

Low Temperature Wurtz-Type Polymerization of Substituted Dichlorosilanes

Inorganic High Polymers

Inorganic High Polymers

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