| Prediction of Cleavage Sites for Polymers in SIMS by MO Calculations |
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* Department of Chemistry, Faculty of Science, Kanazawa University (Kanazawa 920-1192, Japan) |
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| The cleavage sites of representative polymers in time-of-flight(TOF)- and static(S)-secondary ion mass spectrometry (SIMS) can be estimated from the two-center bond energies of the electric neutral model oligomers by semiempirical MO calculations using the AM1 method in MOPAC software. The cleavage of the intramolecular bonds may be classified into three cases; a) the scission can occur in any bonds [polyethylene, poly-(vinyl methyl ether), polyacrylonitrile, poly(vinyl alcohol)], b) the cleavage of the main chain occur in any bonds, after pendant groups break first [poly(vinyl chloride), poly(acrylamide)], c) the main chain carbons with the pendant group break in any bonds of the main chain [poly(vinyl floride), poly(tetrafluoroethylene)]. Examples of the cleavage are also used in secondary positive-ion fragment spectra of conductive polymers. Furthermore, we analyze the decomposition process of nitrocellulose (NC) due to X-ray induced surface damage by the MO calculations using the electric neutral dimer model. The scission of NO2 groups in the NC is confirmed from the TOF-SIMS measurement. | ||
| Key words: Secondary Ion Mass Spectroscopy (SIMS), Semi-empirical MO, Positive secondary ions, Bond energy, Polymer | ||
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