Polymer surface analysis, peak

Figure 33.2 shows XPS spectra of the surfaces of the TMS plasma polymer film deposited on (Ar + H2) plasma-pretreated steel (a, b, c) and on O2 plasma-pretreated steel (d, e, f). As shown in the spectra, the surface of the plasma film is functional in nature with functional groups of C-OH, C=0, and Si-OH. Two films basically ended up with the same surface structure. This is also confirmed by XPS analysis of the film during the film aging in air after the film deposition, which indicated that the film surfaces were saturated with a fixed surface structure after a few hours of air exposure [4]. This is due to a well-known phenomenon that the residual free radicals of the plasma polymer surface reacted with oxygen after exposure to air [5]. Curve deconvolution of C Is peaks showed structures of C-Si, C-C, C-0, and C=0. The analysis clearly shows a silicon carbide type of structure, which is consistent with the IR results. The functional surfaces of TMS films provide bonding sites for the subsequent electrodeposition of primer (E-coat). 

A control experiment entailed immersion of the cyclic imide functionalized plasma polymer surface into THF at 25 °C for 1 h. No changes in the infrared spectrum were observed (not shown). The intermediate amide functionalized plasma polymer surface was also exposed to a solution of cyclopentadiene in THF at 25 °C for 1 h. Infrared analysis showed spectral features similar to those described above for the imide surface, the main difference being the peak between 1800 and 1600 cm indicating the presence of amide rather than imide linkages at the surface. Finally, the plasma polymer surface functionalized with cyclic imide groups was exposed to [(trimethylsilyl)methyl]cyclopentadiene solution in cyclohexane at 25 °C for 1 h. Two new bands appeared at 2975 and 2890 cm characteristic of the asymmetric CH3 stretching and the symmetric CH3 stretching (Fig. 19.3, spectrum c). 

Figure 8 Positive ion ToF-SiMS spectrum from the surface of pretreated (electrochemically oxidized) polypropylene, illustrating the typicai signai-to-noise ratio of poiymer fragments at low mass and additive molecular ions at high mass (see text). The peak at nVz133 is due to primary Cs+ ions. Reproduced with permission from Vanden Eynde X (2001) Quantitative analysis of polymer surfaces. In Vickerman JC and Briggs D (eds.), ToF-SIMS Surface Analysis by Mass Spectrometry, Ch.16. Manchester SurfaceSpectra/IM Pubiications SurfaceSpectra/IM Publications.)...

Most importantly, with regard to polymier surface analysis, XPS also prorides chemical state information particularly in the C Is region. Fi re 4 shows a high resolution scan of the C Is spectrum of poly lactic acid (PLA), and each of the three separate chemical emironments within the polymer gives rise to a peak in the C Is envelope. The fig ure also demonstrates a deconvolution of the envelope using Gaussian peaks and it is found that the three peaks have identical areas, reflecting the concentrations of these environments in the poly mer. 

There the SSIMS (Fig. 93 A) and the FABMS (Fig. 93 B) secondary positive ion spectra are compared for PTFE the surface of the PTFE has to be coated with a gold film for SSIMS measurement but not for FABMS. More fragment ions occur in the SSIMS spectrum than in FABMS, and in the FABMS spectrum the size of the peak at m/e=12 (C ) relative to the principal peak at m/e = 69 (CI ) is much smaller than in SSIMS. indicating much less damage of the polymer surface during FABMS analysis. 

X-ray photoelectron spectroscopy (XPS) XPS is a surface analysis technique that can be used to ascertain surface elemental composition and types of bonds present on the surface. It is also a straightforward, easy, and non-destructive characterization technique. In XPS, different scan resolutions lead to different information. On the one hand, a low-resolution scan can provide the percent of each element, as well as their atomic concentrations. On the other hand, a high-resolution scan can give the types of bonds and concentrations on the surface. Take carbon (Cis) as an example, its high resolution scans can be divided into four components peaks around 285.0, 286.5, 228.0, and 289.5 eV. These subpeaks are Cl (C-C or C-H), C2 (C-OH), C3 (O-C-O or C=0), and C4 (0-C=0), respectively. XPS has frequently been applied to confirm the chemical changes of polymer or fiber after treatment. In addition. XPS can be used to verify the occurrence of surface... 

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