DYNAMIC INFRARED

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

Perhaps, the most dramatic example of the effects of drawing on the spectra of a polymer comes from the stress-induced crystal transition of poly(butylene terephtha-late) 292,29 298 299). The phase transition of PTMT has been investigated above and below the glass transition temperature by means of dynamic infrared measurements... 

Rector, K.D., Jiang, J., Berg, M.A., and Payer, M.D. (2001) Effect of solvent viscosity on protein dynamics infrared vibrational echo experiment and theory, J. Phys. Chem. 105, 1081-1082. 

This behaviour is reminiscent of dynamical averaging seen in NMR spectroscopy, which is treated using a Bloch-equation analysis. Turner and coworkers were the first to use this type of analysis of dynamic infrared spectra to calculate rate constants and self-isomerisation barrier heights in the case of a turnstile -type exchange of CO ligands observed in trigonal bipyramidal [(q -diene)Fe(CO)3] complexes. In a similar fashion, rate constants for electron transfer in the ruthenium cluster dimers were calculated from the lineshapes of the (—1) states. As expected from the electrochemical data, the rate constant was fastest for the most electronically coupled dimer (1) and slowest for the... 

A method for determining kinetic parameters from dynamic infrared data was developed to overcome the problems listed above (A). Through the use of constant temperature ramps, appropriate instrument software (6) (Sheen, C. W. Snyder, R. W. Computers Chemistry, in press) and spreadsheet techniques the activation energy and pre-exponential factor for any reacting system can be obtained in a few hours. When performing this dynamic kinetic analysis however there are some effects which must be accounted for... 

Poly(phenoxy phenylene vinylene)(PO-PPV) is synthesized via the chlorine precursor route as shown in Figure 3. The CPR is preferred for preparation of precursor polymers with large substituents such as phenoxy. The precursor film is quite flexible and dynamic infrared linear dichroism (DIRLD) studies (stretching the polymer while recording the dynamic infrared spectra) are in progress. 

Dynamic infrared linear polarised spectra of thermoplastic polyester urethane and nylon-6 films were recorded under a varying sinusoidal strain. Dichroic spectra were calculated from the dynamic polarised spectra. The large bipolar bands in the dichroic in-phase spectra, caused by large frequency shifts of the original monopolar absorption bands, were ascribed to hydrogen bonds. 29 refs. 

DIRLD (dynamic infrared linear dichroic) spectra of prestretched isotactic polypropylene were recorded. The line shape features in the in-phase spectra are described on the basis of frequency shifts and absorption amplitude... 

Anomalous transport behavior was observed, indicated by dynamic infrared spectra and evidence that water diffusion and water-induced polymer relaxation are occurring on similar time scales. 

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. 

Figure 1-3. Schematic diagram of the dynamic infrared linear dichroism (DIRLDi experiment 23], A small-amplitude sinusoidal strain is applied to a sample, and submolecular level reorientation responses of chemical moieties are monitored with a polarized IR beam.

In addition to the time-resolution constraints on dynamic infrared measurements, sensitive instrumentation is also required. The signals of interest, which are often 10" times smaller than the normal IR absorbance of the sample, exist only as a result of the small dynamic strain applied to the sample. 

Ultimate dichroic ratio Dynamic infrared linear dichroism Observation period Time... 

There is a broad agreement that carbene species developed on partly oxidized transition metal ions are necessary to bring about the metathesis reaction. The data reported earlier provide support that the environment of the active site does possess acid properties. It has been proposed that there is a relationship between the Brpnsted acidity of the rhenium-based catalysts and the metathesis activity [52], and that the activity is not related to their Lewis acidity. Dynamic infrared spectroscopic experiments were conducted by poisoning a Re207/Al203 catalyst (8.0 wt% Re) under a propene flow [53], Ammonia adsorption gave rise to coordinated NH3 species, characterized by the bands at 1618, 1326, and... 

Block Diagram of Dynamic Infrared System Based on Rapid Scanning FTIR Spectrometer... 

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. 

DYNAMIC INFRARED LINEAR DICHROISM MEASURED WITH A MONOCHROMATOR... 

Noda showed that the wavenumber-dependent variations of the dynamic dichro-ism may be analyzed by a correlation t hnique. For a pair of DIRLD signals measured at two different wavenumbers, ZV4(vi, f) and AA(v2, t), the dynamic infrared cross-correlation function X(x) is defined as... 

The synchronous correlation intensity, (vi, V2), characterizes the degree of coherence between two signals that are measured simultaneously and is maximized when the variations of the two dynamic infrared dichroism signals are totally in phase with each other and minimized when the two signals are out of phase. Conversely, the asynchronous correlation intensity (vi, V2) characterizes the degree of coherence between two signals that are measured at two different instants that are separated in time by a correlation time x/2co. Thus, the maximum value of... 

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. 

Kischel, M., Kisters, D., Strobe, G., and Veeman, W.S. (1998) Dynamic infrared spectroscopy, a tool to detect hydrogen bonds in polymers Fur. Polym. J., 34, 1571. 

Wang H, Graff D K, Schoonover J R and Palmer R A (1999) Static and dynamic infrared linear dichroic study of polyester/polyurethane copolymer using step-scan FT-IR and photoelastic modulator, Appl Spectr 53 687-696. 

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. 

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