DYNAMIC INFRARED LINEAR SPECTROSCOPY

I. Noda, A.E. Dowrey and C. Marcott, Characterization of polymers using polarization-modulation infrared techniques Dynamic infrared linear dichroism (DIRLD) spectroscopy. 

Noda, L Dowrey, A. E. Marcott, C., Characterization of Polymers Using Polarization-Modulation Infrared Techniques Dynamic Infrared Linear Dichroism (DIRLD) Spectroscopy. In Fourier Transform Infrared Characterization of Polymers, Ishida, H., Ed. Plenum Press New York, 1987 pp 33-57. 

I. Noda, A. E. Dowrey, and C. Marcott, Characterization of polymers using polarization-modualtion infrared techniques dynamic infrared linear dichroism (DIRLD) spectroscopy, in Fourier-Tran orm Infrared Characterization of Polymers, H. Ishida, Ed., Plenum Press, New York, 1987, p. 33. 

Marcott, C. and Noda, I. (2002) Dynamic infrared linear dichroism spectroscopy. In Handbook of Vibrational Spectroscopy, Vol. 4 (eds J.M. Chalmers and PR. Griffiths), John Wiley Sons, Ltd, Chichester, pp. 2576-2591. 

Up to this poinL we have primarily focused our attention on the application of theo-oprical characterization techniques for monitoring the dynamics of supramolecular stmctures, such as the spatial reorganization of crystals and microphase-separated domains, in various polymeric systems under the influence of flow, deformation, and relaxation. We now shift our attention to rheo-oprical analysis at submolecular scale by using molecular spectroscopic probes. In particular, a rheo-oprical technique called dynamic infrared linear dichroism (DIRLD) spectroscopy, capable of monitoring segmental dynamits of polymer chains, is described. 

Figure 1-3 shows a schematic diagram of a dynamic IR linear dichroism (DIRLD) experiment [20-25] which provided the foundation for the 2D IR analysis of polymers. In DIRLD spectroscopy, a small-amplitude oscillatory strain (ca. 0.1% of the sample dimension) with an acoustic-range frequency is applied to a thin polymer film. The submolecular-level response of individual chemical constituents induced by the applied dynamic strain is then monitored by using a polarized IR probe as a function of deformation frequency and other variables such as temperature. The macroscopic stress response of the system may also be measured simultaneously. In short, a DIRLD experiment may be regarded as a combination of two well-established characterization techniques already used extensively for polymers dynamic mechanical analysis (DMA) [26, 27] and infrared dichroism (IRD) spectroscopy [10, 11]. 

Attenuated total reflection (ATR) FTIR is one of the most useful tools for characterising the chemical composition and physical characteristics of polymer surfaces [53]. One useful application is the measurement of molecular orientation using polarised infrared ATR spectroscopy [54,55]. The polarised infrared ATR spectra normally include three-dimensional (e.g., machine, transverse, and thickness direction) orientational information in contrast to the polarised transmission infrared linear dichroism. In addition, band absorbance of less than 0.7 au is easily achieved, even with the strong absorption bands, because the penetration depth of ATR from sample surfaces can be adjusted to a few micrometers by changing the internal reflection element and/or the angle of incidence. If successful combination of the dynamic infrared spectroscopy and the ATR methods can be achieved, more useful dynamic orientational information can be obtained. 

Probing Metalloproteins Electronic absorption spectroscopy of copper proteins, 226, 1 electronic absorption spectroscopy of nonheme iron proteins, 226, 33 cobalt as probe and label of proteins, 226, 52 biochemical and spectroscopic probes of mercury(ii) coordination environments in proteins, 226, 71 low-temperature optical spectroscopy metalloprotein structure and dynamics, 226, 97 nanosecond transient absorption spectroscopy, 226, 119 nanosecond time-resolved absorption and polarization dichroism spectroscopies, 226, 147 real-time spectroscopic techniques for probing conformational dynamics of heme proteins, 226, 177 variable-temperature magnetic circular dichroism, 226, 199 linear dichroism, 226, 232 infrared spectroscopy, 226, 259 Fourier transform infrared spectroscopy, 226, 289 infrared circular dichroism, 226, 306 Raman and resonance Raman spectroscopy, 226, 319 protein structure from ultraviolet resonance Raman spectroscopy, 226, 374 single-crystal micro-Raman spectroscopy, 226, 397 nanosecond time-resolved resonance Raman spectroscopy, 226, 409 techniques for obtaining resonance Raman spectra of metalloproteins, 226, 431 Raman optical activity, 226, 470 surface-enhanced resonance Raman scattering, 226, 482 luminescence... 

If ultrafast nonlinear vibrational spectroscopy [1-3] has recently developed into an important tool providing original informations on the dynamics of weak hydrogen bonds (H-bonds), the simpler linear infrared (IR) vs(X—H) absorption spectroscopy spectra remains, however, to be an important method for the understanding of this dynamics. Considerable experimental and theoretical works have been done in this last field [4—17]. 

We will show in this section that by applying nonlinear infrared methods, such as IR-pump-IR-probe, dynamical hole burning, and IR photon echoes, one can gather significantly more detailed information on the structure and dynamics of the amide I band than is possible with conventional (linear) absorption spectroscopy. Starting with some knowledge of the underlying contributions to amide I absorption, such as obtained by the aforementioned empirical approaches, nonlinear spectroscopy could provide... 

Dias et al., used, what they called, a hyphenated rapid real-time dynamic mechanical analysis (RT DMA) and time resolved near-infi ared spectroscopy to simultaneously monitor photopolymerization of acrylate coating compositions. This allowed them to determine the rate of conversion and the mechanical properties of the finished films. It is claimed that up to 374 near infrared spectra and to 50 dynamic analysis points can be accumulated within a second. They observed that modulus buildup does not linearly follow chemical conversion of acrylate bonds. The gel point is detected after passing a certain critical acrylate conversion. Their experimental data revealed a critical dependence of the mechanical property development during the later stage of acrylate conversion. 

DMA = dynamic mechanical analysis, DMTA = dynamic mechanical thermal analysis, DSC = differential scanning calorimetry, FTIR = Fourier transform infrared spectroscopy, GPC - gel permeation chromatography, LLDPE = linear low-density polyethylene, PMMA = polymethyl methacrylate, TGA = thermo-... 

Linear and nonlinear infrared spectroscopy are powerful tools for probing the structure and vibrational dynamics of molecular systems." In order to take full advantage of them, however, accurate models and methods are required for simulating and interpreting spectra. A common approach for modeling spectra is based on computing optical response functions (ORFs)." Unfortunately, exact calculations of quantum-mechanical ORFs are not feasible for most systems of practical interest due to the large number of DOF. Instead, mixed quantum-classical methods ean provide suitable alternatives." " " ... 

Kortaberria, G., et al.. Curing of an Epoxy Resin Modified with Poly(Methylmethacrylate) Monitored by Simultaneous Dielectric/Near Infrared Spectroscopies. Europ. Polym, J., 2004.40 129-136. Mijovic, J., et al.. Interplay of Segmental and Normal Mode Dynamics in Polymer Networks Undergoing Chemical Cross-Linking. Epoxy/Amine-Terminated Linear and Stai PPO Eormnlations. Macmmolecules, 2003. 36 4589-4602. 

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