Field Desorption Mass Spectra of Polymer Chemicals

Abstract

Abstract From the results presented here, it is clear that FD-MS is a very effective analytical method for determining molecular weights of polymer chemicals. Molecular ions were the only prominent ions produced in the FD mode of analysis for the series of representative polymer chemicals discussed in this paper. Good molecular ion spectra were obtained even from compounds that are quite unstable, both structurally and thermally. It is also evident, on the other hand, that FD-MS by itself provides only limited chemical structure information. The molecular weight is provided and often nothing else. Fortunately the molecular weight and “chemical intuition” regarding the history of the sample in question are often enough to deduce the structure. If not, then other techniques are available to provide complementary information. Electron impact (EI) mass spectra can be run on the same samples to obtain fragmentation patterns, and other spectro-scopic techniques (infrared and magnetic resonance) can be used to provide detailed structural information. Several application areas can be identified in which FD-MS can play an important role in the characterization of nolymer chemicals in industry. These include chemical identification (molecular weight and structure determination), direct detection of components in mixtures, identification of liquid chromatographic (LC) effluents, characterization of polymer blooms and extracts, identification of vapors from polymer processing, and identification of polymer chemical degradation products. For many of these applications the samples to be analyzed are very complex mixtures of chemical compounds. Electron impact mass spectroscopy is quite limited in its ability to analyze such complex mixtures due to the extensive fragmentation (and perhaps decomposition) that takes place in the ion source. Since molecular ions are normally the only prominent ions formed in the FD mode of analysis, FD-MS can be a very powerful tool for the characterization of polymer chemical mixtures. In summary, field desorption mass spectroscopy can in many cases provide molecular weight and structural data for polymer chemicals heretofore not obtainable by any analytical technique. In addition this information complements well the structural data obtained by magnetic resonance, infrared, and electron impact mass spectroscopy. We therefore feel confident that FD-MS will become increasingly important in the characterization of polymer chemicals in the future.