Spectral analysis of eight polymers in SIMS by MO calculation. Prediction of cleavage of polymers and structural formula of the positive-ion fragment

Abstract

Spectra of eight polymers [(CH2-CHR)n (R = H, OH, F, Cl, OCH3, and CONH2), (CF2-CF2)n] and (CH2-CHCN)n in time-of-flight (TOF)- and static(S)-secondary ion mass spectrometry (SIMS), respectively, were analyzed by semiempirical and ab initio molecular orbital (MO) calculations. We predicted where the cleavage of the polymers occurs on sputtering, due to two-center bond energies of the model pentamers by a semiempirical MO calculations using AM1 program; a) the cleavage can occur in any bonds (polyethylene, poly(vinyl methyl ether), polyacrylonitrile), b)the cleavage of the main chain occurs in any bonds, after side chain groups cleaved first (poly(vinyl chloride, poly(acrylamide)), c) the main chain carbons with the side chain group cleave at any bonds of the main chain (poly(vinyl fluoride, poly(tetrafluoroethylene), poly(vinyl alcohol)). We also determined the possible structural formulas of the secondary positive-ion fragments in the range of 0-100 amu by ab initio MO calculations using the HONDO7 program.