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This paper is concerned with the effects that polymer molecular weight, casting solvent, sonification (with a non-polymer solvent) and annealing have upon the secondary ion mass spectrometry (SIMS) of polymers. Films of a series of monodispersed poly(methyl methacrylate) (PMMA) standards, Mw2965–1200000, were prepared by solution casting from four solvents (tetrahydrofuran (THF), 2-butanone, toulene and chloroform) onto clean aluminium (Al) substrates. The PMMA films were characterized by high- and unit-mass resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS). To determine the significance of variations seen in ion intensities, one PMMA sample was re-analysed 24 times, and the scatter in the absolute counts and normalized and ratioed ion intensities for specific (termed ‘key’) positive and negative ions were calculated. This provided 95% confidence error bars, which were subsequently employed. The 95% confidence limits were significantly reduced by normalizing or ratioing. Molecular weight was found to have the greatest effect in the SIMS spectra obtained, with the differences being most marked betweenMw=2965 andMw=89100. This was seen in both the total negative ion counts (m/z31–200) and the key negative ion ratios. An explanation based on the surface concentration of chain ends is presented. Negative ion ratios were shown to be very sensitive to trace amounts of residual solvents. By annealing above the PMMA glass transition temperatureTgsolvent-free films were produced from three solvents and these were spectrally indistinguishable. Solvent-free films could not be produced from THF. Residual solvent was identified by high mass resolution ToF-SIMS. Sonification with hexane, a polymer non-solvent, had a considerable effect on the total negative ion counts (m/z31–200). No concomitant chemical changes were detected, so this effect is thought to arise from a physical perturbation of the surface. © 1997 by John Wiley & Sons, Ltd.

A series of poly(2-hydroxyethyl methacrylate) gels cross-linked with different concentrations of ethylene glycoldimethacrylate were examined by static secondary ion mass spectrometry (BIMB). Changes in the peak intensities of atomic versus molecular secondary ions were observed in negative ion BIMB as a function of cross-linker concentration. These changes in the distribution of secondary ions as a function of cross-linker concentration, and thus as a function of molecular weight between cross-links, are discussed with respect to the factors affecting secondary ion emission during the BIMB process. The sensitivity of static BIMB to the concentration of cross-links in the polymer chains on the surface of the polymer, demonstrated by this study, may advance the study of technologically relevant surface modifications involving surface cross-linking

Films of a series of monodisperse, moderately syndiotactic poly(methyl methacrylate) (PMMA) standards, with Mw ranging from 2,900–428,000, were solution-cast and spun-cast from chloroform onto clean aluminium substrates. The polymers were thoroughly characterized by conventional spectroscopic and chromatographic techniques. The films were studied using x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF SIMS). The effects of molecular weight and film thickness on SIMS spectra were investigated thoroughly by unit-mass and high-resolution ToF SIMS. Film thickness had a pronounced effect on the negative SIMS spectra, particularly in films a few monolayers thick. This was seen in both the total negative ion counts (m/z 31–200) and the key negative ion intensity ratios. A parallel effect was observed with respect to the effect of molecular weight. These differences are attributed to (i) the original end-group concentration in the surface which decreases with increasing molecular weight and (ii) the original end-group concentration in the surface which increases as film thickness decreases.

Poly(ethylene terephthalate)(PET) and polystyrene (PS) have been studied using static secondary ion mass spectrometry (SSIMS). A triple quadrupole analyser has been employed to investigate secondary ion fragmentation and formation mechanisms. Daughter spectra and neutral loss spectra were obtained and fragmentation patterns were deduced. Comparison of the fragmentation data obtained in the gas-phase collisionally activated dissociation (CAD) experiments with the SSIMS data suggested that ion formation probabilities during CAD were similar to ion formation probabilities at the solid surface during low-flux sputtering. It was concluded that low-energy gas-phase CAD processes model effectively the processes which lead to fragmentation of the polymer during low-flux sputtering.

Static SIMS spectra from essentially undamaged acrylic polymers have been obtained for total ions doses of 2 × 1012 ions cm−2. For a series of polymethacrylates the spectra can be interpreted in terms of a constant contribution from the polymer backbone plus dominant fragments from the ester side chain. Isomeric butyl methacrylate polymers can be distinguished. Negative ion spectra reflect the O:C atomic ratio of the bulk polymer. Positive ion relative intensities from ethyl methacrylate: hydroxyethyl methacrylate random copolymers correlate with polymer composition. Previous SIMS data from polymethacrylates have been shown to represent highly damaged surfaces.