New synthetic methods for boron-containing polymers, ceramics and molecular clusters [electronic resource].

Su, Kai.
330 p.
Chemical engineering.
Chemistry, Organic.
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Mode of access: World Wide Web.
Boron-containing molecular clusters, polymers and solid state materials show a number of important bonding, structural, chemical and physical properties. However, one of the major limitations to the development and applications of these materials has been the lack of general synthetic methods by which a specific compound or material can be achieved in high yield or in a desired form. Thus, the overall goal of this thesis work was to develop new efficient synthetic routes to these boron-containing compounds.
Part I. New synthetic routes to boron-containing polymers and solid state materials. Processable poly(B-vinylborazine) and random poly(styrene-co-B-vinylborazine) polymers were prepared by solution free radical polymerization techniques. Molecular weight studies of these polymers suggested polymer structures consisting of linear and branched polymer chains.
The synthesis of new borazine-substituted hydridopolysilazane polymers was achieved by the thermal reaction of borazine with hydridopolysilazane. The modified polymers were converted in high ceramic and chemical yields to SiNCB ceramic composites that exihibit enhanced thermal stabilities and reduced crystallinities.
A new method for the syntheses of metal borides and metal-boride/metal-nitride composites that employs processable metal-oxide or metal powder dispersions in a suitable boron-based polymer was developed. This method has been successfully used to generate metal-boride ceramics in various forms, including powders, compacts and films.
Part II. New synthetic routes to molecular borane clusters. A new synthetic strategy for achieving monocarbon or dicarbon insertions into polyhedral boron cage compounds, involving the reactions of polarized terminal alkynes with polyhedral borane anions, was developed. The use of this approach allowed the synthesis of a number of new types of carborane clusters including di-, tri- and tetracarbon carboranes.
The syntheses of the first seven-vertex nido-carborane zwitterion, exo-6-(Me$\sb3$P$\sp+$-CH$\sb2$)-3,4-Et$\sb2$-nido-3,4-C$\sb2$B$\sb5$H$\sb{5\sp-}$ and the first iminotricarbon carborane, arachno-5-CH$\sb3$-4,5,12,11-C$\sb3$NB$\sb8$H$\sb{11\sp-}$ were achieved by the reaction of closo-2,3-Et$\sb2$C$\sb2$B$\sb5$H$\sb5$ with trimethylmethylenephosphorane and the reaction of nido-5,6-C$\sb2$B$\sb8$H$\sb{11\sp-}$ with refluxing acetonitrile, respectively. The structures of both compounds were confirmed by single crystal X-ray studies.
Source: Dissertation Abstracts International, Volume: 54-06, Section: B, page: 3101.
Supervisor: Larry G. Sneddon.
Thesis (Ph.D.)--University of Pennsylvania, 1993.
Local notes:
School code: 0175.
University of Pennsylvania.
Contained In:
Dissertation Abstracts International 54-06B.
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