Comparison of static secondary ion mass spectrometry, ion scattering spectroscopy, and x-ray photoelectron spectroscopy for surface analysis of acrylic polymers

Abstract

The comparison of three surface analytlcal tools, static secondary Ion mass spectralmetry (SIMS), ion scatterlng spectroscopy (ISS), and X-ray photoelectron spectroscopy (XPS or ESCA), Is presented. Information avallable from ISS and ESCA is Illustrated by comparing plots ol carbon/oxygen Intensity ratio vs. monomer composition for both methods. Both ESCA and ISS yield linear correlations, ESCA having the higher correlation coefficient. The ISS plot had some devlatlons whlch could not be explained by steric effects alone. Statlc SIMS results were interpreted by uslng a "backbone/slde chain" model of polymer structure which explains ions generated from bond breaking along the hydrocarbon backbone and the pendant side chain functlonality which Is varled in the polymer serles of poly( methacrylates). Posltlve Ion spectral patlerns are Interpreted for shorl chain alkyl, Isomeric butyl, and cyclic and long chain alkyl functlonallties.The chemical analysis of polymer surfaces has provided a fruitful realm for the application of X-ray photoelectron spectroscopy (XPS or ESCA) (1,2). ESCA is now well-known for the unique qualitative and quantitative surface information derived from core and valence level spectra. However, when utilized alone, ESCA has some major weaknesses. We have been active in the extenaiion of surface analysis of polymers by ion beam methods: secondary ion mass spectrometry (SIMS) and ion scattering spectroscopy (ISS) (3-5). In the present paper we will coimpare the analytical capabilities of ISS and SIMS in the so-cdled "static" m d e (Le., low primary ion energies and current densities) with ESCA for the analysis of poly(methacrylates) where the pendant ester group is varied in both length and functionality.Static SIMS analysis of organics has been furthered by the use of a cooled probe technique to analyze frozen liquids. These substances have yielded a varieity of SIMS results. Ions assigned to peaks in the low mass range (0-100 amu) were explained by simple fragmentation of' molecules (bond breaking) as the dominant mechanism (6, 7), with rearrangement ("polymerization") (6) occurring after i9 long bombardment time. High mass results (0-1000 amu) indicated cluster ion formation, with significant rearrangement, could explain most spectral features (8). Since relative intensities of high mass cluster ions decreased logarithmically, it is possible that the peaks cannot be seen under typical detection conditions employed in t hLe low mass studies. Thus it appears that spectral results for the low mass range from 0 to 200 m u , employed in this study, will be dominated by ions directly related to the structure of organic molecules from bond breaking (4, 7) with low intensity rearrangement phenomena accounting for high mass molecular ions. The use of "destructive" methods of analysis like ISS and SIMS requires consideration of the effects on the sample integrity of the method itself. The analysis conditions described (4) were chosen because of indications that moderate to high primary ion beam energies...

Preparation and Surface Properties of Acrylic Polymers Containing Fluorinated Monomers

“…Similar spectra have been observed with other polymer compositions. Such a step profile has been observed and predicted during other surface segregation studies on miscible polymer mixtures. −

6 DSIMS depth profile for fluorine-modified acrylic polymer 3a (1.5 wt % 1 ; single shot). The polymer film was measured to be 370 Å thick on a silicon wafer.

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“…Cursory investigations of the acrylic copolymers modified by addition of 1 revealed that the primary fragmentation pathway is quite different from typical hydrocarbon acrylate polymers. 35 Unlike hydrocarbon acrylate polymers, the positive ion spectra of the (perfluoroalkyl)ethyl methacrylate-modified polymers contained no information about the fluorotelomer end groups. Therefore, the discussion will concentrate on negative ion spectra.…”

“…Such a step profile has been observed and predicted during other surface segregation studies on miscible polymer mixtures. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] It is the magnitude (excess) of fluorine at the surface and gradient normal to the surface which will determine the ultimate repellency and durability properties of these (perfluoroalkyl)ethyl methacrylate-modified polymers. It is important to note the differences in fluorine atom concentration differences provided by the ESCA data (∼20-70-fold excess) compared to the DSIMS depth profiling data (∼10-fold excess).…”

Analysis of polymer surfaces by SIMS 17. An assessment of the accuracy of the mass assignment using a high mass resolution ToF‐SIMS instrument

“…For all spectra, the accuracy of the mass assignment was calculated for each peak listed in Tables 1, 2 and 3 according to the formula (3) This yields the absolute value of the mass accuracy (A) in parts per million calculated from the measured mass (mmea) and the exact mass (mex) of the species.…”

Static Secondary Ion Mass Spectrometric Analysis of Langmuir—Blodgett Film Multilayers

“…Gardella and Hercules used SIMS to distinguish between members of a homologous series of poly(alkyl methacrylates) based on length, chemical identity, or isomeric nature of the ester side chains. Electron Spectroscopy for Chemical Analysis (ESCA) could not differentiate between members of this series (7,2). These distinctions can also be made using attenuated total reflectance infrared spectroscopy (ATR-IR), however the greater sensitivity and shallower sampling depth (down to 10 A) of SIMS make it uniquely useful when information on the uppermost region of a sample surface is desired.…”