Fourier transform dielectric spectroscopy

Poly(vinyl acetate). The dielectric and mechanical spectra of hybrids produced by mixing a poly (vinyl acetate)—THF solution with TEOS, followed by the addition of HC1 have been investigated (45). Mixtures were made which were believed to be 0, 5, 10,15, and 20 wt °/o Si02, respectively. These composites were transparent and Fourier transform infrared spectroscopy (ftir) revealed hydrogen bonding between the silicate network and carbonyl units of the poly(vinyl acetate) (PVAc). No shift in the T of the composites from that of the pure PVAc was observed. Similady, the activation... 

In order to actually cover 19 decades in frequency, dielectric spectroscopy makes use of different measurement techniques each working at its optimum in a particular frequency range. The techniques most commonly applied include time-domain spectroscopy, frequency response analysis, coaxial reflection and transmission methods, and at the highest frequencies quasi-optical and Fourier transform infrared spectroscopy (cf. Fig. 2). A detailed review of these techniques can be found in Kremer and Schonhals [37] and in Lunkenheimer [45], so that in the present context only a few aspects will be summarized. 

The inclusion of the polymers in the composites was confirmed by Fourier transform infrared spectroscopy. The dielectric constants of PVK-montmoril-lonite hybrids are improved relative to the homopolymer from 3-6 to 60-180 in the frequency range of 0.1-25 kHz. 

In addition to PALS, other spectroscopic techniques that have heen used to investigate physical aging are electron spin resonance spectroscopy (ESR) [83], fluorescence spectroscopy [84—86], dielectric spectroscopy [87], and Fourier-transform infrared spectroscopy (FTIR) [88]. 

The elastic contribution is also called elastic incoherent structure factor (EISF). It may be interpreted as the Fourier transformed of the asymptotic distribution of the hopping atom for infinite times. In an analogous way to the relaxation functions (Eq. 4.6 and Eq. 4.7), the complete scattering function is obtained by averaging Eq. 4.22 with the barrier distribution function g E) obtained, e.g. by dielectric spectroscopy (Eq. 4.5)... 

DSC is increasingly being applied to the study of epoxy resin cure in combination with other analytical methods such as nuclear magnetic resonance and Fourier transform infra-red spectroscopy, chromatographic methods, and dynamic mechanical or dielectric studies. It is probably as part of such combined investigations that DSC can be used most effectively in basic research, and in quality control and assessment. 

It is not possible to discuss all the methods available for characterizing foods critically and systematically in a single volume. Methods pertaining to interfaces (food emulsions, foams, and dispersions), fluorescence, ultrasonics, nuclear magnetic resonance, electron spin resonance, Fourier-transform infrared and near infrared spectroscopy, small-angle neutron scattering, dielectrics, microscopy, rheology, sensors, antibodies, flavor and aroma analysis are included. 

There are also more recent developments of other dual physio-chemical experimental methods. For example Durand et al (2006) presented a laboratory-made system that allows the coupling of dielectric analysis and Fourier-transform near-infrared spectroscopy (FT-NIR) to follow the cure of polyepoxy reactive systems. Complementary data are provided by the simultaneous dielectric analysis (the vitrification phenomenon) and near-infrared spectroscopic analysis (the extent of the reaction). 

This chapter treats principally the vibrational spectra determined by infrared and Raman spectroscopy. The means used to assign infrared absorption bands are outlined. Also, the rationale for the selection of permitted absorption bands is described. The basis for the powerful technique of Fourier Transform Infrared (FTIR) is presented in Appendix 6A. Polyethylene is used to illustrate both band assignment and the application of selection rules because its simple chain structure and its commercial importance have made polyethylene the most thoroughly studied polymer. The techniques of nuclear magnetic resonance, neutron inelastic scattering and ultraviolet spectroscopy are briefly described. The areas of dielectric loss and dynamic mechanical loss are not presented in this chapter, but material on these techniques can be found in Chapters 5. 

One of the methods used to study emulsions has been the use of dielectric spectroscopy. The permittivity of the emulsion can be used to characterize an emulsion and assign a stability (1,42,48—54). The Sjoblom group has measured the dielectric spectra using time-domain spectroscopy (TDS) technique. A sample is placed at the end of a coaxial line to measure total reflection. Reflected pulses are observed in time windows of 20 ns, Fourier transformed in the frequency range from 50 MHz to 2 GHz, and the complex permittivity calculated. Water or air can be used as reference sample. The total complex permittivity at a frequency (co) is given by ... 

Friedrich Kremer is Professor of Molecular Physics, Materials Research Spectroscopy, Institute of Experimental Physics I, University of Leipzig, Germany. His research interests include broadband dielectric spectroscopy, time-resolved Fourier transform infiared (FHR) spectroscopy, and experiments with optical tweezers. In 2005 he was awarded with the Karl Heinz Beckurts - Prize in 2011 he received the Wol%ang-Ostwald-Prize from the German Colloid Society. 

Products were characterized by Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), ultraviolet visible (UV-Vis) spectrophotometry, scanning electron microscopy (SEM), and broadband dielectric/impedance spectroscopy (BDS). New absorption bands were observed corresponding to the conjugated pol5mieric units by FTIR-ATR and UV-Vis spectrophotometric analysis. The influence of concentration of PEDOT-PSS and PEDOT on the composite electrospun nanofibers was studied by EIS. Morphologies of electrospun nanofibers were also investigated by SEM. 

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