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The aim of this paper is twofold: first to report on the lateral and vertical characterisation of a surface chemical gradient of carboxylic-acid functionality and second, to demonstrate the use of said gradient to probe the passive adsorption of immunoglobulin G (IgG) as a function of the density of surface carboxylic-acid groups. A surface chemical gradient of carboxylic-acid functionality was fabricated by the plasma copolymerisation of octadiene (OD) and acrylic acid (AA). The plasma-polymerised gradient was over 12 mm, with 2 mm of plasma-polymerised OD at one end and 2 mm of plasma-polymerised AA at the other. By means of linescan angle resolved x-ray photoelectron spectroscopy (ARXPS) it is shown precisely how acid functionality varies from the 2 mm position (OD end) on the gradient to the 10 mm position (AA end). By recording data from 16 angles at each of the 25 sampling points along the gradient, it is shown that the surface gradient also changes vertically, most notably in the thickness of the plasma polymer. At the OD end the plasma-polymerised layer is 6.3 nm thick, while at the AA end the plasma-polymerised layer is 5 nm. More subtle changes in chemistry through the plasma-polymerised layer are shown at the 7.5 and 10 mm points. An identical gradient is used to probe IgG adsorption along the length of the gradient. ARXPS is used to monitor the nitrogen Is (N1s) signal at 25 points, the N1s signal being unique to adsorbed IgG. It is demonstrated that IgG adsorbs in far greater amount (IgG per unit area) at the OD end, and the amount of adsorbed IgG decreases along the length of the gradient. It is estimated that >200 ng/cm 2 adsorbed at the OD, while at the AA the amount adsorbed was

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.

Plasma polymers (PPs) have been prepared from methyl vinyl sulphone (MVS), ethyl vinyl sulphone (EVS) and vinyl sulphone (VS). The ratio of radio frequency (r.f.) power (W) to flow rate of monomer (F) or W/F is an important parameter in plasma polymerization. PPs prepared at low and high W/F were analysed by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and grazing angle infra-red (PAIR) spectroscopy. XPS revealed that significant quantities of the sulphone group had been retained from the monomer. The greatest retention was observed in the PPs that had been prepared at low W/F, where the majority of the sulphur was present as RSO 2 R/H

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been employed to monitor the chemical changes occurring with continuous UV irradiation in the surface region of neat films of polystyrene and the copolymer of styrene and 2-(2-hydroxy-3-vinyl-5-methylphenyl)benzotriazole (HVB, 2% w/w). Previous conclusions concerning the relative rates of oxygen uptake of these systems have been confirmed. New data are presented that enable delineation of two different surface reactions and demonstrate activation of the polymer surface by HVB with respect to polymer degradation as well as oxygen uptake. Some conclusions are drawn concerning the mechanism by which this activation is achieved.

Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS) have been employed to study the plasma surface oxidation of poly(ether etherketone) (PEEK). The positive and negative ion ToF-SIM spectra obtained from a cleaned PEEK surface were easily interpreted using conventional mass spectrometry rules. Plasma oxidation of PEEK was found to prodoce complex positive and negative ion spectra. In these spectra, ions diagnostic of the PEEK repeat unit were much reduced in intensity, and new ions diagnostic of plasma treatment were introduced

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) studies, utilizing both laterial imaging and shallow depth profiling, of a 50 :50 poly(vinyl chloride)/poly(methyl methacrylate) (PVC :PMMA) blend have confirmed the presence of a thin overlayer of PMMA on the phase-separated bulk morphology.