Calorimetry introduction

Cross-linking constrains the conformational flexibility of biopolymers and, as a rule, stabilizes their secondary, tertiary, and quaternary structures against the denaturing effects of high temperatures.29 We used differential scanning calorimetry (DSC) to compare the heat-induced conformational transitions of selected RNase A samples that were characterized in Figure 15.2. A brief introduction to DSC is provided in Section 15.15.1 for those readers unfamiliar with this biophysical method. Trace 1 in Figure 15.3a is the heat absorption... 

G. Hohne, W. Hemminger and H.J. Flammersheim, Differential Scanning Calorimetry An Introduction for Practitioners. Berlin Springer-Verlag, 1996. 

The enthalpies of phase transition, such as fusion (Aa,s/f), vaporization (AvapH), sublimation (Asut,//), and solution (As n//), are usually regarded as thermophysical properties, because they referto processes where no intramolecular bonds are cleaved or formed. As such, a detailed discussion of the experimental methods (or the estimation procedures) to determine them is outside the scope of the present book. Nevertheless, some of the techniques addressed in part II can be used for that purpose. For instance, differential scanning calorimetry is often applied to measure A us// and, less frequently, AmpH and AsubH. Many of the reported Asu, // data have been determined with Calvet microcalorimeters (see chapter 9) and from vapor pressure against temperature data obtained with Knudsen cells [35-38]. Reaction-solution calorimetry is the main source of AsinH values. All these auxiliary values are very important because they are frequently required to calculate gas-phase reaction enthalpies and to derive information on the strengths of chemical bonds (see chapter 5)—one of the main goals of molecular energetics. It is thus appropriate to make a brief review of the subject in this introduction. 

J. J. Christensen, J. Ruckman, D. J. Eatough, R. M. Izatt. Determination of Equilibrium Constants by Titration Calorimetry Part I, Introduction to Titration Calorimetry. Thermochim. Acta 1972, 3, 203-218. 

Note The terms isothermal and adiabatic as applied to reactions (and reaction calorimeters) do not have the same meaning here as when used by thermochemists. The excellent introduction to reaction calorimetry by Skinner, Sturtevant and Sunner should be consulted (Skinner et al., 1962). 

In the course of calorimetry study of hydrolysis ofTi(OR)4, at different concentrations and h ratios the values of enthalpies of hydrolysis reaction were measured (-AHJ at 298.15K as 14.2, 64.9, 19.3 kJ/mol for R = Et, Pr, Bun respectively [660], These values grow linearly at the first stage when h increases from 0 to 1 and practically do not undergo any changes with further introduction of water. Therefore, the first step of hydrolysis should be regarded as reaction with stoichiometry of h = 1 ... 

Hohne, G., Hemminger, W. and Flammersheim, H.-). (1995) Differential Scanning Calorimetry an Introduction for Practitioners, Springer, Berlin. 

This monograph provides an introduction to scanning ther-moanalytical techniques such as differential thermal analysis (DTA), differential scanning calorimetry (DSC), dilatometry, and thermogravimetric analysis (TG). Elevated temperature pyrometry, as well as thermal conductivity/diffusivity and glass viscosity measurement techniques, described in later chapters, round out the topics related to thermal analysis. Ceramic materials are used predominantly as examples, yet the principles developed should be general to all materials. 

Agilent Technologies 2003. Palo Alto, California, Agilent Technologies Impedance Measurement Handbook (December) www.optics.arizona.edu/Palmer/OPTI380B/PDFdocs/5950-3000.pdf. Allais, C., Keller, G., Lesieur, P., Ollivon, M., Artzner, F. 2003. X-ray diffraction/calorimetry coupling. A new tool for polymorphism control. J. Thermal Anal. Cal. 74, 723-728. Barnes, H.A., Hutton, J.F., Walters, K. 1989. An Introduction to Rheology. Elsevier, Amsterdam. 

In relation to the questions addressed in the introduction, the following answers are given, based on experimental results obtained for three polymer systems investigated in thin layers using broadband dielectric spectroscopy, capacitive scanning dilatometry, and calorimetry ... 

A complete characterization of liquid crystalline polymers should include at least two aspects the characterization of the molecular structure and that of the condensed state structure. Since the first characterization is nothing more than what is practiced for non-liquid-crystalline polymers, we will restrict the discussion to only a short introduction of methods mostly used in the characterization of the presence and the main types of polymeric liquid crystal phases. The methods include the mostly used polarizing optical microscopy (POM, Section 4.1), differential scanning calorimetry (DSC, Section 4.2) and X-ray diffraction (Section 4.3). The less frequently used methods such as miscibility studies, infrared spectroscopy and NMR spectroscopy will also be discussed briefly (Section 4.4). 

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