Attenuated total reflection fundamentals

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

Fig. 3 Schemes of fundamental hollow waveguide (HWG) structures. ATR attenuated total reflection...

To aid the general reader, short descriptions of the fundamentals of modern Raman scattering and attenuated total reflection (ATR) infrared spectroscopy are provided. This is followed for each spectroscopy by brief introductions to the enhancement mechanism involved. 

The combination of infrared spectroscopy with the theories of reflection has made advances in surface analysis possible. Attenuated Total Reflectance (ATR) spectroscopy is an innovative technique for proving chemical information of a sample surface and the ability to quantify newly formed species, based upon Pick s second law. The fundamentals of attenuated total reflection (ATR) spectroscopy date back to the initial work of Jacques Fahrenfort and N.J. Harrick, both of whom independently devised the theories of ATR spectroscopy and suggested a wide range of applications. The schematic showing ATR-FTIR configuration is illustrated in Fig. 1 (KS. Kwan, 1998). The penetration depth, d, can be estimated as ... 

IR-transmitting optical fibres are evanescent wave sensors using a mathematical deconvolution technique to extract the absorbances and follow the concentrations of the components as they occur in both laboratory scale and process production. The fibre-optic probe used can be placed at specific locations within the samples or at the surface. The specificity of the technique, the speed of data acquisition and the portability of equipment make this method ideal as a tool to fundamentally probe polymer reactions and processes. Chalcogenide optical fibres are used to direct IR radiation from an FUR spectrometer through an attenuated total reflection (ATR) probe immersed in a reactor and back to the spectrometer. 

Specific interactions in binary blends of ethylene-vinyl acetate copolymer with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron acceptor ability of the resin, by using attenuated total reflection FTIR spectroscopy. Molecular acid-base were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and equilibrium constant of pair formation were obtained. A crystalline transition of the EVA copolymer was observed and discussed in terms of enthalpy and entropy considerations based on FTIR and calorimetric DSC investigations. Fundamental results are then summarised to predict the interfacial reactivity of such polymer blends towards acid or basic substrates. 16 refs. 

The mid-IR spectral range contains much denser and more selective information compared to the near-IR, where overtone and combination bands of the fundamental molecular vibrations occur. As the intensity of bands in the mid-IR is higher, optical path lengths are on the micrometer scale. Such path lengths can be achieved with a special technique that uses attenuated total reflection, and which renders optical materials compatible with aqueous biofluids. Recently, dry films of biosamples of nanoliter volumes have been successfully applied for reagent-free... 

Fundamental for the characterization of polymer grafting surface are microscopy techniques, i.e. Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Attenuated Total Reflection-Eourier transform infrared spectroscopy (ATR-FTIR spectroscopy). 

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