Infrared Spectroscopy microstructure

A number of techniques have been employed that are capable of giving information about amorphous phases. These include infrared spectroscopy, especially the use of the attenuated total reflection (ATR) or Fourier transform (FT) techniques. They also include electron probe microanalysis, scanning electron microscopy, and nuclear magnetic resonance (NMR) spectroscopy. Nor are wet chemical methods to be neglected for they, too, form part of the armoury of methods that have been used to elucidate the chemistry and microstructure of these materials. 

C.E. Miller, B.E. Eichinger, T.W. Gurley and J.G. HermiUer, Determination of microstructure and composition in butadiene and styrene-butadiene polymers by near-infrared spectroscopy. Anal. Chem., 62, 1778-1785 (1990). 

In earlier literature reports, x-ray data of a-based ceramics, the /3-like phase observed in certain silica minerals was explained by a structural model based on disordered Q -tridymite. However, others have suggested that the structure of the stabilized jS-cristobalite-like ceramics is closer to that of a-cristobalite than that of Q -tridymite, based on the 29Si nuclear magnetic resonance (NMR) chemical shifts (Perrota et al 1989). Therefore, in the absence of ED data it is impossible to determine the microstructure of the stabilized jS-cristobalite-like phase. ED and HRTEM have provided details of the ceramic microstructure and NMR has provided information about the environments of silicon atoms in the structure. Infrared spectroscopy views the structure on a molecular level. 

Infrared spectroscopy has been used successfully to determine the microstructure of CTPB prepolymers (10). Representative analysis for the microstructure of each of the four prepolymers presently available is shown below ... 

The methods quoted under a) above give bulk information only although they may be used in conjunction with composite models to test theories of the microstructure. The methods under b) are more closely related to structural elements. It is an interesting fact that even at the atomic level, displacement and therefore strain can be measured by several means (although average values are of course obtained) yet loads are only measurable in terms of the secondary effects they produce, for example elastic or inelastic displacements, strain-related optical effects or electronic transitions detectable by optical or infrared spectroscopy. The problem of load transference in a polymer is of great interest, yet very few methods exist by which it may be studied. 

Miller, C.E., Eichinger, B.E., Gurley, T.W. and Hermiller, J.G., Determination of Microstructure and Composition in Butadiene and Styrene-Butadiene Polymers by Near-Infrared Spectroscopy Anal. Chem. 1990, 62, 1778-1785. 

Chemical characterisation of F uptake in archaeological bone has already been developed in the 19th century [1,2] and is now well established [60], However, relatively few studies use a combined multianalytical approach using trace elemental and microstructure analytical techniques (PIXE/PIGE, TEM-EDX) for evidencing modifications on different microscopic and nanoscopic levels (Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), SEM, TEM) and enabling an objective evaluation of the F uptake mechanisms [32-34,51],... 

It is concluded that IR spectroscopy provides information on qualitative as well quantitative analyses of rubbery materials, apart from their microstructures (that is, whether cis or trans, syndiotactic, atactic or isotactic). Different types of rubber blends (compatibilised or self-crosslinked) can be identified by the infrared spectroscopy. Synthesis, and degradation of polymers can also be followed by IR spectra. Mechanism of interaction between rubbers and fillers, can also be studied by IR-spectra. Different types of chemical reactions like the milling behaviour of rubbers, mechanism of adhesion and degradation can also be studied with the help of IR spectroscopy. The technique plays a great role in the product analysis under reverse engineering. 

Infrared spectroscopy is one of the most important tools used to characterise the chemical structure, composition and microstructure of different polymers [8-10]. In earlier chapters, the principles and applications of infrared (IR) spectroscopy in the characterisation of rubbers have been discussed. This chapter describes how IR spectroscopy can be used to characterise different types of chemically modified elastomers. 

In terms of characterizing the microstrac-ture of polymer chains, the two most useful techniques are infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy. Commercial infrared spectrometers were introduced after the end of the second world war and quickly became the workhorse of all polymer synthesis laboratories, providing a routine tool for identification and, to a certain degree, the characterization of microstructure (e.g., the detection of short chain branches in polyethylene). In this regard it can no longer compete with the level of detail provided by modem NMR methods. Nevertheless, IR remains useful or more convenient for certain analytical tasks (and a powerful tool for studying other types of problems). So here we will first describe both techniques and then move on to consider how they can be applied to specific problems in the determination of microstructure. 

Although infrared spectroscopy was one of the first tools applied to the characterization of polymer microstructure, for many tasks it has been supplanted by NMR spectroscopy. In about a page or so briefly outline why this is so. 

Infrared spectroscopy has been extensively used in elucidating the microstructure of plasma-polymerized materials. Earlier works (54, ) have shown that short alkane segments and various types of vinyl groups are the predominant structural groups observed. 

Copolymers with sites for association in aqueous solutions were pre-pared by copolymerizing acrylamide with N-alkylacrylamides or with the ampholytic monomer pairs sodium 2-acrylamido 2 methylpro-panesulfonate (NaAMPS) and 2-acrylamido-2-methylpropane-dimethylammonium chloride (AMPDAC). The copolymers were characterized by elemental analysis, NMR and Fourier transform infrared spectroscopy, and lowhangle laser and quasielastic lightscattering measurements. Rheological properties were studied as a function of microstructure, molecular weight, polymer concentration, electrolyte concentration, and shear rate. On the basis of those results, a conceptual model that is based on microheterogeneous domain formation in aqueous solutions is proposed. 

Infrared spectroscopy is a widely used method to characterize polymers and copolymers. However, for determination of the composition and microstructure... 

The chain microstructure has a very important influence on the properties of TPEs. As mentioned earlier, production of SBS or SIS with a high 1,4 content is necessary. TPO properties also depend quite heavily on any deviations of the microstructure from the ideal head-to-tail, pure isotactic, or syndiotactic microstructure. Properties such as tacticity, cw-trans isomerization, and copolymerization content are usually characterized using NMR. Peak positions and peak intensities are used to quantitatively ascertain microstructure to a high degree of accuracy. Copolymer composition can also be determined using NMR. Infrared spectroscopy can also be employed to determine microstructural characteristics in some polymers. 

Two series of cellulose samples, Avicel and Whatman CFll cellulose ball-milled powders with different crystallinity are studied below Tg temperature by using positron annihilation lifetime spectroscopy. A good correlation is found between ortho-positronium formation probability and crystallinity as measured by Fourier transform -infrared spectroscopy. Sub-nanometer hole distributions are found to be narrowed as a function of milling time. These are interpreted in terms of microstructural changes of cellulose. 

It is known that far-infrared (FIR) spectra give direct information on phonon modes and impurity levels in the crystal lattices. Infrared spectroscopy enable us also to obtain information about real crystalline microstructure and interior interactions of the semiconductor solid solutions (Barker Sievers, 1975 Robouch et al.,2001). 

Innocenzi, Infrared Spectroscopy of Sol-Gel Derived Sihca-Dased Films A Spectra-Microstructure Overview, J. Non-Cryst. Solids, 316,309-319 (2003). 

Qian et al. conducted a study on bamboo particles (BP) that were treated with low-concentrations of alkali solution for various times and used as reinforcements in PLA based composites [35]. Characteristics of BP by composition analysis, scaiming electron microscopy, Brunauer-Emmett Teller test, and Fourier transform infrared spectroscopy, showed that low-concentration alkali treatment had a significant influence on the microstructure, specific surface area, and chemical groups of BP. PLA/treated-BP and PLA/untreated-BP composites were both produced with 30 wt% BP content. Mechanical measurements showed that tensile strength, tensile modulus, and elongation at break of PLA/BP composites increased when the alkali treatment time reached... 

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