TFAA chemical derivatization and XPS. Analysis of OH and NHx polymers

Abstract

The determination of functional groups on complex polymer surfaces by X-ray photoelectron spectroscopy (XPS) can be improved considerably by derivatization reactions. Simple polymers containing hydroxyl groups or amino groups were investigated as reference materials for the derivatization with trifluoroacetic anhydride (TFAA).Poly(vinyl alcohol) (PVA), poly(hydroxyethyl methacrylate) (PHEMA), poly(vinyl butyral) (PVB), poly(allylamine) (PAAm), and poly(diallyl amine) (PDAAm) were derivatized using TFAA and analyzed with XPS. Polyethylene (PE) was used as an independent external reference for the binding energy (BE). Applying this procedure, the BE scales of all measurements were referenced to the carbon atoms of PE. It was found that the BE of the CF 3 component in the C1s region is different when bonded as an acetate or as an amide. The CF 3 BE is also influenced by the density of these groups in the polymer molecule. In TFAA-PVA, where every second main chain carbon atom carries a trifluoroacetate (TFAc) group, the BE is 294.3 eV while in TFAA-PVB with only isolated groups, the BE is 293.6 eV. The BE of the CF 3 component in the trifluoroacetamides (TFAAms) prepared from PAAm and PDAAm was found to be 292.5 and 292.3 eV, respectively. Compared with the analog fluorine free compounds, the BE is shifted toward higher values also for the ester carbon atom, the amide carbon atom, and the carbon atom to which the ester or amide is bonded.The data suggest that the gas phase reaction of TFAA with a polymer surface is diffusion limited. The actual ester or amide formation is a fast reaction and runs as a wave into the surface.

Fabrication, Characterization, and Comparison of Oxygen-Rich Organic Films Deposited by Plasma- and Vacuum-Ultraviolet (VUV) Photo-Polymerization

“…As already pointed out in section 2.3.1., the hydroxyl concentration, [OH], has been of particular interest here. Therefore, we used the chemical derivatization reaction with trifluoro acetic anhydride (TFAA), known to selectively react with the OH functionality when only O –containing functional groups are present . L‐PPE:O and UV‐PE:O films deposited using N 2 O as a source of heteroatoms were hence excluded from this part of the study due to the possibility of competing reactions with N‐containing functional groups.…”

“…Of particular interest in this work, like in our earlier studies relating to nitrogen‐rich (L‐PPE:N) coatings, has been the quantification of a particular type of functionality; while that was the primary amine concentration, [NH 2 ], the hydroxyl concentration, [OH], has been the one of interest here. For this purpose, we used the chemical derivatization reaction with trifluoro acetic anhydride (TFAA): …”

“…In principle, the XPS survey scan and the high resolution core level spectra offer two different protocols to quantify the concentration of OH groups. Gross and Pippig introduced two different quantification methods for (OH) labeling using elemental composition and C1s peak‐fit, namely Quantitative‐Elemental‐Analysis (QEA) and Peak‐Fit‐Analyses (PFA), respectively.…”

X‐ray photoelectron analysis of surface functional groups on diamond‐like carbon films by gas‐phase chemical derivatization method

“…[49] Holländer et al distinguished the TFAA-derivatized OH and NH 2 groups in the corresponding polymer films by the curve-fitting analysis of the C 1s spectra. [47,48] Thus it has been difficult to obtain the correct evaluation of the surface functional groups by using only the GCD method. In this work, we have performed the surface analysis of DLC films by using the GCD method with the help of a mathematical treatment.…”

Multimode Surface Functional Group Determination: Combining Steady-State and Time-Resolved Fluorescence with X-ray Photoelectron Spectroscopy and Absorption Measurements for Absolute Quantification

“…1,2 Whereas for the latter NMR, IR, conductometry or zeta-potential measurements can be employed for direct surface group analysis, 3,4 macroscopically flat substrates are significantly more demanding to analyze due to their low surface-tovolume ratio and often require employment of a specific chemical label that can be interrogated selectively and sensitively. 5-7 Analysis of such substrates is mainly performed with sophisticated surface analytical techniques like X-ray photoelectron spectroscopy (XPS) [8][9][10][11][12][13] or time-offlight secondary ion mass spectrometry (ToF-SIMS). 14,15 Obtaining quantitative information on surface functional groups, however, is rather challenging as these techniques mostly produce relative results.…”