CHARACTERIZATION OF POLYSILOXANES WITH DIFFERENT FUNCTIONAL-GROUPS BYTIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY

Polydimethylsiloxane (PDMS), polyhydromethylsiloxane (PHMS), and polym ethylphenylsiloxane (PMPhS) have been studied by TOF-SIMS to investiga te effects of functional group changes on polymer fragmentation mechan isms. Cyclic fragments are observed in the low mass range spectra of P DMS and PHMS, but not in the spectrum of PMPhS. Effects of functional group substitution on the fragmentation mechanisms of polysiloxanes ar e evident in the high mass range spectra (>1000 Da). Peaks of oligomer s cationized by silver dominate the high mass range of the spectra of all low molecular weight polysiloxanes. However, fragmentation pattern s of these samples are different. Neutral cyclic fragments cationized by silver are identified in the high mass range of the spectra of PDMS and PHMS, but not in the spectrum of PMPhS. The major fragments of PH MS and PMPhS are [oligomer-14+Ag](+). The PHMS spectrum also shows pea ks [oligomer-28+Ag](+). These distinctive fragmentation patterns can b e used to identify the polysiloxanes. (C) 1998 American Society for Ma ss Spectrometry.