Kristin Trommer

Silicon Carbide — A Survey of Synthetic Approaches, Properties and Applications

The challenge to develop tailor-made precursor molecules for silicon carbide has significantly intensified the progress in synthesis of organosilicon polymers. A critical overview is presented regarding useful synthesis routes towards such molecules with appropriate chemical composition as well as controllable architecture (metal condensation of halogenosilanes or silahalogenocarbons, disproportionation of disilanes, dehydrocoupling of hydrosilanes, hydrosilylation of olefins).

Reaction of the SiCl bond with trialkyl orthoformates preparation of alkoxy-substituted silanes

Abstract Trialkyl orthoformates in the presence of aluminium chloride represent quite useful reagents to generate silicon alkoxides from chlorosilanes. 3-Cyanopropyltrichlorosilane and 2-[(2-trichlorosily)ethyl]-pyridine give the triethoxy compounds 3-cyanopropyltriethoxysilane and 2-[(2-triethoxysilyl)ethyl]-pyridine respectively. Via this route, in methylchlorooligosilanes a partial or complete exchange of the chlorine substituents for alkoxy groups occurs depending on the starting molar ratio of silane:HC(OR)3 (R  Me, Et). SiCl2Me groups react to SiClMe(OR) first before SiMe(OR)2 groups are formed. (Si)2 SiClMe units are not affected by HC(OR)3.

Preparation and NMR spectroscopical investigations of (diethylamino)(methoxy)-methylchlorodi– and –trisilanes

Abstract Starting from the methylchlorodisilanes SiClMe 2 –SiClMe 2 , SiCl 2 Me–SiCl 2 Me and methylchlorotrisilanes SiClMe 2 –SiClMe–SiClMe 2 and SiCl 2 Me–SiClMe–SiCl 2 Me the stepwise reaction with first HC(OMe) 3 /[AlCl 3 ] and second HNEt 2 leads to the formation of (diethylamino)(methoxy)-methylchlorooligosilanes. The products were investigated by means of 29 Si, 1 H NMR spectroscopy and GC/MS measurements.

New olefinic functionalized disilanes. Synthesis and NMR spectroscopical investigations

Abstract The new olefinic substituted aminodisilanes, which are obtained from the reaction of organometallic reagents with aminochlorodisilanes, are converted into the chlorodisilanes by equilibration reactions or treatment with HCI. The resulting olefinic functionalized disilanes are identified by means of 29Si, 13C, 1H NMR and GC MS measurements.

Processing and Properties of Carbon Nanotube PVC Composites

Commercially available multiwalled carbon nanotubes (MWCNT) were incorporated in coating masses based on PVC by means of three roll mill. The best results could be obtained using the 5 µm gap. Thin PVC sheets were formed via knife coating having an electrical conductivity up to 1,500 S/m that are applicable as electric heating elements. For the use in the antistatic range, CNT contents ≤0.5% are sufficient. Rheological measurements indicate the quality of particle processing. AFM investigations are suitable to investigate the alignment of the nanoparticles in the bulk polymer. Using this method, the decrease of agglomerates as well as the splitting of CNT bundles within further mass processing could be visualized.

Preparing of Heatable, CNT-Functionalized Polymer Membranes for Application in Textile Composites

The electrically induced heating of textile composite materials is already applied in the clothing and outdoor use. However, making thin, flexible and washable heating layers remains a challenge. Based on various polymers thin electrically heatable polymer sheets were developed using multi-walled carbon nanotubes as electrically conductive fillers in silicone, polyurethane as well as polyvinylchloride. To prepare the membranes a knife coating process was applied. The viscosity of the polymer masses, the particle alignment, the percolation as well as the electrically and heating properties of the membranes were investigated.

Thin Polymer Layers with Superparamagnetic Properties

Superparamagnetic particles were widely used in medical applications as well as for magnetic sensors and actuators. Generally, the size of the particles is in the range of 10–20 nm. To use such particles in large-scale applications, a simple processing as well as the use of commercially available particles is required. Therefore superparamagnetic nanoparticles available on the market were incorporated in flexible polymer films and the magnetic properties of the films were investigated. At ambient temperature no significant hysteresis was observed, indicating the superparamagnetic properties. Films containing up to 25% nanoparticles were prepared. The films show a saturation magnetization of 13.8 Am2/kg and a coercivity of 7 Oe at ambient temperature.

New Organosilicon Precursors for the Formation of Porous Structures

Mono- and disilane substituted arene-centered star molecules are prepared via reactions of halogenodialkylaminosilanes with lithium aryl acetylides. After complete coupling of both chlorosilane and acetylenic synthon the dialkyl-amino substituent can be replaced by halogenes. Reactive sites at the silicon atoms allow an enlargement of the system by coupling and cross-linking to build up a permanent cavity structure. All compounds have been characterized by NMR-spectroscopy.