Broadband dielectric spectroscopy samples

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... 

Additional information on ferroelectric and electroclinic switching can be obtained with broadband dielectric spectroscopy. It appears that the molecular dynamics of FLCPs are comparable to those of low molecular weight compounds [67]. However, the experimental observations are made more difficult for FLCPs than for low molecular weight SmC liquid crystals due to the conductivity contribution which takes place at frequencies below 10" Hz and to the difficulty to get a macroscopically well-aligned sample. 

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). 

BordaUo HN, Zakharov BA, Boldyreva EV, Johnson MR, Koza MM, Seydel T, Fischer J (2012) Application of incoherent inelastic neutron scattering in pharmaceutical analysis relaxation dynamics in phenacetin. Mol Pharm 9 2434-2441 Bptker JP, Karmwar P, Strachan CJ, Cornett C, Tian F, Zujovic Z, Rantanen J, Rades T (2011) Assessment of crystalline disorder in cryo-milled samples of indomethacin using atomic pairwise distribution functions. Int J Pharm 417 112-119 Boutonnet-Fagegaltier N, Menegotto J, Lamure A, Duplaa H, Caron A, Lacabanne C, Bauer M (2002) Molecular mobihty study of amorphous and crystalline phases of a pharmaceutical product by thermally stimulated current spectrometry. J Pharm Sci 91 1548-1560 Bras AR, Noronha JP, Antunes AMM, Cardoso MM, Schdnhals A, Affouard Fdr, Dionfsio M, Correia NIT (2008) Molecular motions in amorphous ibuprofen as studied by broadband dielectric spectroscopy. J Phys Chem B 112 11087-11099... 

The set-up of a broadband dielectric spectroscopy (BDS) experiment is displayed in Fig. 2. The sample is placed between two electrodes of a capacitor and polarized by a sinusoidal voltage U(co). The result of this phenomena is the orientation of dipoles which will create a capacitive system. The current 1(cp) due to the polarization is then measured between the electrode. The complex capacity C(cp) of this system is describe by the complex dielectric fxmction e(u>) as ... 

Broadband dielectric spectroscopy has been utilized in many forms to study the dynamics of polymers under strong states of confinement. These include all the major modes of confinement discussed previously, including thin film, nano-porous, nanofiUer, and nanosUucture confinements. This is a testament to the utility of broadband dielectric spectroscopy. It is relatively straightforward to design a sample configuration... 

Dielectric spectroscopy is a very promising tool to probe relaxation processes, especially since new broadband equipment can cover frequencies in the range of lO"" to 10 ° Hz. The theoretical introduction of this technique can be found in literature (Korhonen et al. 2008). Basically, electrodes of two different sizes are used, and the overall response, given by capacitance (C), depends on both the intrinsic characteristics (permittivity e) and the geometry of the sample. The relationship between capacitance and sample geometry is given by ... 

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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