ToF-SIMS quantification of polystyrene spectra based on principal component analysis (PCA)†

Abstract

Monodisperses polystyrenes (PS) with molecular weight (Mn) ranging from 850 to 20000 g mol‐1 and with different butyl end‐groups have been analysed by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS). Only the fingerprint part of the spectra (m/z<200) has been considered. This part comes from the fragmentation of the macromolecules and this is the only contribution in the secondary ion spectra of bulk polymers. In a former study, it has been shown that Mn has a significant influence on the PS secondary molecular ion intensities. It was found that not only the end‐group characteristic ion intensities are modified for Mn<50000 g mol‐1, but also those related to main chain fragments. In this study, the possibility to use this effect to quantify the molecular weight of the macrochains at the surface is investigated. Because the quantification method should preferably include all the information contained in the spectra (over 150 peaks), statistical methods are needed. Principal component analysis is applied to these ToF‐SIMS data. Principal component analysis builds the best linear combination of the variables, namely the principal components that describe the greatest amount of variation of the sample set. It is found that only one principal component is required to account for the molecular weight variations and a second one allows the samples to be discriminated depending on their butyl end‐groups. Whatever the PS end‐groups (linear, secondary or tertiary butyl), the correlation found between the first principal component and the sample molecular weight leads to the definition of a universal curve that allows the molecular weight determination for an unknown monodisperse PS sample. © 1997 John Wiley & Sons, Ltd.

Time‐of‐flight mass spectrometric analysis of ion formation in hypervelocity impact of organic polymer microspheres: comparison with secondary ion mass spectrometry, 252Cf mass spectrometry and laser mass spectrometry

“…We compared TOF‐SIMS spectra of positive and negative ions from literature data for polystyrene,6,, 7 see Table 1(b). As expected, all ion types are quite unspecific.…”

“…For comparison with SIMS we used PEDOT as aqueous suspension, (‘Baytron P’ by Bayer Chemicals, Leverkusen, Germany), which was prepared by drying it on a clean silver foil. SIMS comparison for polystyrene was taken from the literature, both positive ions6 and negative ions 7…”

Static secondary ion mass spectrometry (S-SIMS) Part 1: methodology and structural interpretation

“…Principal component analysis applied to virtually all fragments below m/z 200 from monodisperse PS with MW between 850 and 20000 and different butyl end groups showed potential for end group and M n determination (Vanden Eynde & Bertrand, 1997). The ®rst principal component was primarily related to the MW according to an exponentially increasing relationship and nearly independent of the end group.…”

Graft photopolymerization of polyethylene glycol monoacrylate (PEGA) on poly(methyl methacrylate) (PMMA) films to prevent BSA adsorption

“…A description of the PCA principles applied to SIMS is given in Ref. [17]. PCA is performed on all the peaks in PMMAox and PEGA-treated PMMAox spectra to discern PMMAox and PEGA characteristic fragments, respectively.…”