Novel oligomers possessing a backbone formed of ((TRIPLE BOND)Si(SINGLE BOND)CH2(SINGLE BOND)Si(TRIPLE BOND)) and (SINGLE BOND)Si(SINGLE BOND)n units were prepared by the copolycondensation of bis(chlorosilyl)methanes and various dichlorosilanes in the presence of sodium, in refluxing toluene. The effect of the respective molar ratios of comonomers on the yields and the structure of the copolymers was investigated. The role of substituents on silicon atoms in the ability of these materials to provide convenient ceramic precursors upon pyrolysis was examined. When (TRIPLE BOND)Si(SINGLE BOND)H bonds were present, thermal cross-linking was readily performed and ceramics possessing variable C/Si ratios were prepared.

Novel polycarbosilazanes possessing Si−CH2 Si N linkage in their backbone are described. Their preparation involves thermal cross-linking of poly[(dimethylsilylene)-co-(1,3-dimethyl-1,3-disilazane)]s at 300 350 C. Thus, under controlled conditions, soluble and fusible preceramic polymrs were obtained. Upon pyrolysis, these materials gave good yields of silicon carbonitride-based ceramics containing low free carbon percentages and controlled nitrogen proportions.

A trans-silylation route to 1,3-dichloro-l,3-dihydridodisilazanes, a novel class of polyfunctional disilazane, is described. Thus, heating hexamethyl- or heptamethyl-disilazane under reflux in the presence of an excess of dichlorohydrogenosilane R1SiHCl2, led to compounds of formula (R1ClHSi)2NR2 (R1 = Me, Et, Vi or Ph and R2 = H; R1 = Me and R2 = Me) in high yield. The exchange of chlorinated organosilicon moieties was strongly facilited by a catalytic amount of (πBu4N)F. Interpretation of the results and a few chemical properties of these novel disilazanes are reported.

Ten models of functional poly(carbosilane) (PCS) or poly(carbosilazane) (PCSZ) precursors, prepared from chlorinated poly[(dimethylsilylene)methylene], were pyrolyzed, under inert gas flow or vacuum at temperatures up to 2300-degrees-C, to derive relations between the nature of the precursors and that of the ceramic residues. The organometallic/inorganic transition and the recrystallization of the pyrolytic residues were studied by different analytical techniques. Linear precursors resulted in low ceramic yields unless a cross-linking treatment was applied prior to pyrolysis. High C content precursors do not necessarily lead to high C content ceramics. Ternary (Si-C-O or Si-C-N) and even quaternary tetrahedral species were present in the ceramic residues. Nitrogen was found to inhibit the crystallization of the ex-PCSZ ceramics up to approximately 1400-degrees-C. Only part of the initial skeleton of the precursors was maintained in the ceramics.

To study the mechanisms of pyrolysis of poly(carbosilanes), as well as the effect of the structure of these precursors upon properties of the resulting ceramics, novel organosilicon polymers with well-defined skeletons were prepared. Thus, linear poly(carbosilanes) formed of exactly alternate silicon atoms and methylene groups were synthesized. Owing to the presence of functional groups on silicon centers, cross-linking of these compounds was then investigated according to chemical routes, by creating disilane, disilazane, disiloxane, and hydrocarbon bridges between different poly(carbosilanic) sites. These polymers were characterized by physicochemical methods (IR, NMR, GPC, and TGA).

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNew polycarbosilane models. 2. First synthesis of poly(silapropylene)Eric Bacque, Jean Paul Pillot, Marc Birot, and Jacques DunoguesCite this: Macromolecules 1988, 21, 1, 34–38Publication Date (Print):January 1, 1988Publication History Published online1 May 2002Published inissue 1 January 1988https://pubs.acs.org/doi/10.1021/ma00179a008https://doi.org/10.1021/ma00179a008research-articleACS PublicationsRequest reuse permissionsArticle Views200Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

A method for synthesizing novel linear polysilmethylenes of general formula Me(HMeSiCH2)xSiMe2H (VIIx) is described. This strategy involves the cocondensation of chloromethylsilanes HMe2Si(CH2SiMeH)mCH2Cl (m = 0 or 1) with methyldichlorosilane and 1,3-dichloro-1,3-dimethyl-1,3-disilapropane, respectively, by Grignard reactions. Thus, short-chain polycarbosilanes possessing terminal dimethylhydrogenosilyl groups were prepared (2 ≤ χ ≤ 5). They were then converted into the corresponding chlorinated derivatives Me(Cl MeSiCH2)xSiMe2Cl (VIIIx by reaction with CCl4 in the presence of a palladium catalyst. The mass spectra (70 eV) of both series reveal that characteristic fragmentations occur. Moreover, the SiH-containing derivatives VIIx exhibit analogous behavior during their rearrangement under electronic impact and during their pyrolysis.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTNew polycarbosilane models. 1. Poly[(methylchlorosilylene)methylene], a novel, functional polycarbosilaneEric Bacque, Jean Paul Pillot, Marc Birot, and Jacques DunoguesCite this: Macromolecules 1988, 21, 1, 30–34Publication Date (Print):January 1, 1988Publication History Published online1 May 2002Published inissue 1 January 1988https://pubs.acs.org/doi/10.1021/ma00179a007https://doi.org/10.1021/ma00179a007research-articleACS PublicationsRequest reuse permissionsArticle Views237Altmetric-Citations63LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

AbstractThe oligomeric silanes (V) are prepared by coupling the α,ω‐dichlorosilanes (IV) with the silylmethylmagnesium chlorides (III).

Thermolysis of linear or cyclic polydimethylsilanes into polycarbosilanes by Yajima's method has been studied by analyzing the gases evolved by means of gas chromatography and mass spectroscopy. About 20% of silicon was eliminated as methylsilanes during the reaction. Furthermore these results suggest some differences in the mechanisms of reactions with and without catalyst, as in the structures of the polycarbosilanes obtained.