Dielectric Analysis Methods

Morris et al. [1.126] proposed to use dielectric analysis (DEA) to predict the collapse temperature of two component systems. The background of DEA is explained and the take off frequency (TOF) is chosen as the best analytical method to identify the collapse temperature. Figure 1.55.5 shows the dielectric loss factor as a function of the frequency. 

Morris et al. [1.126] proposed the use of dielectric analysis (DEA) to predict the collapse temperature of two-component systems. The background of DEA is explained and the >take-off frequency< (TOF) is chosen as the best analytical method to identify the collapse temperature. Figure 1.55.5 shows the dielectric loss factor as a function of the frequency. The frequency at the minimum of this curve is called TOF by the authors. TOF varies with the temperature as shown in Figure 1.55.6. The extrapolated intersection of the two linear portions identifies the collapse temperature. The predicted Tc by TOF for 10% sucrose, 10% trehalose, 10% sorbitol and 11% Azactam solution deviates from observations with a freeze-drying microscope (Table 1 in [1.126]) to slightly lower temperatures, the differences being -3, -1.4, 2.2 and 0.7 °C. 

One of the requirements in MALDI-MS analysis is the use of a liquid matrix. The electrowetting-on-dielectric (EWOD) method has been used to move and mix droplets containing proteins and peptides with the liquid matrix, all of which were situated at specific locations on an array of electrodes. With this method, insulin (1.75 pM), insulin chain B (2 pM), cytochrome c (1.85 pM), and myoglobin (1.45 pM) have been analyzed [518]. 

Coming to the present volume, one aim has been to provide a basis on which the student and researcher in molecular science can build a sound appreciation of the present and future developments. Accordingly, the chapters do not presume too much previous knowledge of their subjects. Professor Scaife is concerned, inter alia, to make clear what is the character of those aspects of the macroscopic dielectric behaviour which can be precisely delineated in the theoretical representations which rest on Maxwell s analysis, and he relates these to some of the general microscopic features. The time-dependent aspects of these features are the particular concern of Chapter 2 in which Dr. Wyllie gives an exposition of the essentials of molecular correlation functions. As dielectric relaxation methods provided one of the clearest models of relaxation studies, there is reason to suggest that dipole reorientation provides one of the clearest examples of the correlational treatment. If only for this reason, Dr. Wyllie s chapter could well provide valuable insights for many whose primary interest is not in dielectrics. 

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). 

The application of dielectric constant techniques to thermophysical measurement of solids has been used for a number of years (114, 115). The early uses of the technique involved isothermal measurements employing bridge methods. Recently, techniques have been developed that permit the measurement of the dielectric constant of a solid as a function of temperature, in a manner similar to other TA techniques. Chiu (116) used the term dynamic electrothermal analysis (ETA) to describe the measurement of both the capacitance and the dissipation factor of polymeric samples. Nottenburget al (117) developed an automated technique that permitted the rapid determination of the dielectric properties of a substance over a wide range of temperature and frequencies. This technique, which was called dynamic dielectric analysis (DDA), was modified to measure concurrently the DTA curve of the sample as well (117, 118). This new technique was called dynamic dielectric analysis-differential thermal analysis, DDA-DTA,... 

W. E. Courtney, Analysis and evaluation of a method of measuring the complex permittivity and permeability of microwave insulators, IEEE Trans. Microwave Theory Tech. 18 (1970) 476-485. B.W. Hakki and P.D. Coleman, A Dielectric Resonator Method of Measuring Inductive Capacities in the Millimeter range, IEEE Trans. Microwave Theory Tech. 8 (1960) 402-410. 

E. Motyl. Space Charge in Solid Dielectrics Analysis of Measurement Methods and Investigations. D. Sci. Thesis, Wroclaw, 2000. 

The authors make several qualitative remarks in an attempt to relate the hydrophobicity of the IL cations or anions, the dielectric constant of the organic solvents, or other solvent properties to their experimental results. Although interesting as such, these qualitative comments have their limits and we would like also to commend the efforts of the authors to analyze their data with the slope-analysis method, taking into account more than one equilibrium (see Section 8.3 for a discussion on this method). 

Recently, the investigation of polymer brushes has been focused on the synthesis of new tethered polymer systems primarily through surface-initiated polymerization (SIP). Previously, the term polymer brushes has been limited to the investigation of block copolymers (qv) or end-functional linear polymers that have been physically or chemically adsorbed to surfaces, respectively (3,4). Recent synthetic efforts using different polymerization mechanisms have resulted in the discovery of many novel properties of polymer brushes. This has been aided no less than the use of innovative and unique surface-sensitive analysis methods as applied to flat substrates and particles. The study of polymer brushes has benefited from improved dielectric, optical, spectroscopic, and microscopic characterization methods. Understanding the chemistry of these grafting reactions and how... 

Dynamic mechanical (DMA) and dielectric analysis (DEA) methods are used both to study molecular relaxation processes in polymers and to determine inherent... 

Although the above approaches may all be amenable to detection of crystallization in finished products, they can also be used to characterize the HME (i.e., prior to downstream processing). Further, many other techniques are often applied exclusively to the HME intermediate. For instance, optical microscopy offers excellent detectability of crystalline material in transparent extrudates. Dielectric analysis (DBA Alie et al. 2004 Bhugra et al. 2007, 2008) and thermally stimulated current IR spectroscopy (Shah et al. 2006 Rumondor and Taylor 2010), atomic force microscopy (ATM Lauer et al. 2013 Marsac et al. 2012 Price and Young 2004), and calorimetric methods have also been used to detect crystallization from an amorphous matrix (Baird and Taylor 2012 Pikal and Dellerman 1989 Avella et al. 1991). 

In addition to an examination of the frequency response of series and parallel components of the circuit impedance/admittance, another approach may be particularly valuable. This analysis method involves plotting the real versus imaginary parts of some such complex quantity as admittance or impedance as parametric functions of frequency. Such Argand or "circle diagrams" have been used for many years in electrical engineering when complex dielectric constant is the quantity considered, they are known as Cole-Cole plots. ... 

Dielectric Analysis Based on Lumped Circuit Methods Frequency Response and Impedance Analysis... 

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