Broadband dielectric spectroscopy temperature

Broadband Dielectric Spectroscopy provides a direct experimental access to the molecular relaxations of polymers over a broad frequency and temperature range. It is also especially suitable for the investigation of thin polymer films, because it does not suffer sensitivity loses with decreasing sample amount. This technique does require a special sample preparation for thin films, because of the need to have metal electrodes and good electrical contacts at both interfaces. Spin-coating, one of the most commonly employed methods for the preparation of... 

For thin polystyrene films annealed for 12 hours at 150 °C in high vacuum (10-6 mbar) and measured in a pure nitrogen atmosphere the dynamic glass transition was characterized using two experimental techniques capacitive scanning dilatometry and Broadband Dielectric Spectroscopy. Data from the first method are presented in Fig. 15a, showing the real part of the complex capacity at 1 MHz as a function of temperature for a thin PS film of 33 nm. 

Does a shift of the glass transition temperature reflect a change in the relaxation time distribution or in its mean value only This makes a fundamental difference underlining the power of microscopic techniques like Broadband Dielectric Spectroscopy. 

Broadband dielectric spectroscopy (BDS) is a versatile experimental tool to study the dynamics of polymeric systems. In its modem form it covers the extraordinary frequency range from 10 Hz to 10 Hz with the option to extend both limits to lower and higher values, respectively. This enables one to analyse the molecular d3mamics on a large time scale especially if the temperature of the sample is varied as well. In the present review article examples will be discussed for polymers of widely varying molecular architectures (linear and cyclic chains, star-branched systems, and liquid crystalline polymers). 

In this chapter broadband dielectric spectroscopy (BDS) is employed to polymeric blend systems. In its modem form BDS can cover an extraordinary broad frequency range from 10 " to 10 Hz. Therefore, molecular and collective dipolar fluctuations, charge transport, and polarization effects at inner phase boundaries can be investigated in detail including its temperature dependence. 

Figure 15 Imaginary part e" vs. frequency for amorphous poly(ethylene terephtalate) at temperatures as indicated in K (temperature steps 2.5 K). The solid line is the fit using two superimposed Havriliak-Negami relaxation functions. If not indicated, the error bars are not larger than the size of the symbols. Taken from Kremer, F. Schdnhals, A. In Broadband Dielectric Spectroscopy Kremer, F. Schonhals, A., Eds. Springer, 2003 Chapter 4 with permission.

Broadband dielectric spectroscopy were performed to characterize molecular motion in P4FST homopolymer and copolymer based on 2-(2,4-difiuorophenyl)-l,l-dicyanoethylene (TSE) with 4-fiuostyrene [88], The goal of this study is to explore the incorporation of fiuorinated TSE units in the dielectric properties of these copolymers and to establish the structure-properties relationship. The temperature is ranging from -150°C to 300°C and a frequency interval from 0.001 to 10 Mhz. 

Modem broadband dielectric spectroscopy is a very useful tool to interrogate the molecular dynamics of polymers because response over a broad frequency range from the milli- to giga-Hertz region is possible (10). Therefore, motional processes which take place in polymers on extremely different time scales can be investigated vs. temperature. Moreover, the motional process depends on the morphology of the system. 

Broadband dielectric spectroscopy is a powerful technique for the investigation of physical effects occurring in polymers and polymer composites, such as molecular mobility, polarization, conductivity, interfacial phenomena, phase changes, polymerization, crystallization, etc. [9], Presented results are aimed only at room temperature measurements of conductivity and dielectric permittivity. The measurements of the electrical conductivity o, real and imaginary part of dielectric... 

Mapesa, E.U., Tress, M., Schulz, G., Huth, H., Schick, C., Reiche, M., Kremta-, F. Segmental and chain dynamics in nanometric layers of poly(cis-l,4-isoprene) as studied by broadband dielectric spectroscopy and temperature-modulated calorimetry. Soft Matter 9 (44), 10592-10598 (2013)... 

Sample Preparation and Dielectric Spectroscopy Measurements. Dielectric relaxation spectra were collected using a Novocontrol GmbH Concept 40 broadband dielectric spectrometer over the frequency range 0.01 Hz - 3 MHz and over the temperature range of 0 to 100° C. The temperature stability of the instrument was controlled to within 0.2° C. 

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