Larry Frazier Hanneman

Alkyl- and arylsilsesquiazanes: effect of the R group on polymer degradation and ceramic char composition

A series of alkyl- and arylsilsesquiazanes [RSi(NH)3/2] was prepared by the ammonolysis of the corresponding RSiCl3. Each polymer was pyrolysed to 1200° C in an inert atmosphere to give amorphous Si-C-N ceramic chars. The major volatile products in the pyrolysis effluent were identified and quantified by a combination of TGA-GCMS, TGA-GCFTIR and pyrolysis-capillary GC techniques. Mechanistic aspects correlating the alkyl/aryl group on the polymer structure, decomposition and ceramic char composition were studied. Oxidative stability of the ceramic chars fits percolation theory. The oxygen contents of ceramic chars containing ⩽ 25 wt% carbon increased 1 to 2% after 12 h at 1200° C. At higher levels of carbon the chars were completely oxidized to SiO2.

Decomposition of fluorosilicone stationary phases in solution

Abstract The fluorosilicone stationary phases SP-2401, OV-210, and QF-1 (FS-1265) readily decompose in acetone solution. This decomposition may be catalyzed by residual catalyst and/or the glass surface of the container. Solution decomposition may be prevented by choosing a solvent that is a poorer promoter than acetone or by using a strong acid ion-exchange resin to stabilize the acetone solution.

Analysis of Some Organosilicon Compounds in Biological Materal

The analytical chemical experience gained in the analysis in biological material of the compound 2,6-cis-diphenylhexamethyl-cyclotetrasiloxane (KABI 1774, CisobitanR) and the products formed following its biotransformation is discussed. Quantitative analysis was performed with the highly selective technique of gas chromatography- mass spectrometry (GC-MS), enabling the determination of concentrations down to 0.1 µg/ml of serum. The extraction of this rather lipophilic compound from serum samples into organic solvents was very slow, and to achieve quantitative extraction a homogeneous extraction technique using heptane containing methanol followed by the addition of water was developed. Contamination problems due to the volatility of the organosilicon compound are discussed. Mass fragmentography and mass chromatography were used to unequivocally identify five products formed following the biotransformation of 2,6-cis (in rat, monkey and man), i.e., dimethylsilanediol, methylphenylsilanediol, trimethylphenylsiloxanediol and phenol, all identified as their trimethylsilyl derivatives. The M.S. data were compared to those obtained from similarly derivatized authentic samples. In these studies radioactively labelled substrate was used as an aid for coarse separation of the metabolites and stable isotope labelling was an aid in confirming the source of dimethyl-silanediol as various amounts of this compound appeared in the blanks. Possible metabolic and chemical routes leading to the formation of the breakdown products are briefly discussed.