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Characterization of degradation products of poly[(3,3,3-trifluoropropyl)methylsiloxane] by nuclear magnetic resonance spectroscopy, mass spectrometry and gas chromatography
Authors:Hanspeter Kä  hlig,Peter Zö  llner
Affiliation:a Institute of Organic Chemistry, Vienna University, Währinger Straße 38, 1090 Vienna, Austria
b Bayercropscience GmbH, Product Technology, Industriepark Höchst, G836, D-65926 Frankfurt/Main, Germany
c Department of Clinical Pharmacology, Medical University Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
Abstract:Poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) was treated with the solvents acetone, ethyl acetate and methanol and its degradation products were analyzed with multiple techniques. 1H, 29Si and 19F nuclear magnetic resonance (NMR) spectroscopy were useful for the characterization of the intact polymers and for the determination of cyclosiloxanes. Cyclosiloxanes with a ring size of up to 23 were quantified by gas chromatography. The only degradation products found were TFPmethyl-cyclosiloxanes. 1,3,5,7-Tetrakis(TFPmethyl)-cyclotetrasiloxane was predominant, and (TFPmethyl)cyclotri-, penta- and hexasiloxane could be detected at lower concentrations. The identity of cyclic degradation products with a ring size of up to 6 was unambiguously confirmed by direct infusion mass spectrometry. The TFPmethyl-cyclosiloxanes were successfully ionized by electrospray ionization in the negative mode. None of the techniques applied gave hints to other degradation products such as short linear oligomers. Almost complete degradation of PTFPMS occurred in acetone and methanol, while degradation is distinctly reduced in ethyl acetate.
Keywords:29Si NMR spectroscopy   19F NMR spectroscopy   Mass spectrometry   Degradation   Cyclosiloxanes   Stationary phases for GC
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