Relaxation spectrometry

Relative viscosity Relaxation Relaxation spectrometry Relays... 

Robinson, B.H. (1974). In Chemical and Biological Applications of Relaxation Spectrometry, Wyn-Jones, E. (ed.), D. Reidel Publishing Co., Boston... 

Eigen, M., De Maeyer, L. Theoretical basis of relaxation spectrometry. In Investigation of rates and mechanism of reactions. Part II. Hammes, G. G. (ed.). Techniques of chemistry. Vol. VI. New York Wiley-Interscience 1974... 

Eigen, M., and K. Kustin, The study of very rapid reactions in solution by relaxation spectrometry. ICSU Rev., 5, 97-115 (1963). 

Eigen and his colleagues went deep into biochemistry in the 1960s. They could measure enzyme mechanisms. They could measure the single steps in multi-step reactions and they called their method relaxation spectrometry. As a result of these studies they realized that the enz TOe reactions are optimal. They are fast, as fast as possible, but this is only one aspect. In fact, there are two counteracting principles to consider. One is that the enzyme has to be very specific for its substrate. This is a very specific catalysis and only this way can a complex reaction scheme be controlled. 

E. (2002) Conductometric and electrooptic relaxation spectrometry of hpid vesicle electroporation at high... 

Kakorin, S. and Neumann, E. (2002) Electrooptical relaxation spectrometry of membrane electroporation in lipid vesicles. Colloids and Surfaces A, IW (2-3), 147-165. 

Bianchin, B., Chrisment, J., Delpuech, J. J., Deschamps, M. N., Nicole, D. and Serratrice, G. (1975). In Proceedings of the NATO Advanced Study Institute Chemical and Biological Applications of Relaxation Spectrometry (E. Wyn-Jones, ed.) p. 365. D. Reidel Publishing, Dordrecht, Holland... 

The treatment presented thus far applies to systems where only one independent variable is subject to relaxation. Frequently, however, m > 1) such variables are needed to describe the relaxation properties of interest. Under these circumstances, a set of m relaxation equations of the type given in Eq. [4] can be established. Accordingly, m relaxation times are determined and in a specific relaxation process each relaxation time will contribute its share to the overall effect in proportion to a corresponding amplitude. The ensemble of relaxation times and amplitudes is called the relaxation spectrum of the process under consideration. It reflects the underlying molecular rate mechanism. Thus, in principle, experimental relaxation spectrometry offers a way to elucidate kinetic mechanisms. 

According to DSC, WAXS, as well as relaxation spectrometry data, the investigated blends have a clear two-phase strucmre with PA6 crystallites free of a foreign material. 

As it was found by relaxation spectrometry, r spAe shifts by 5-15°C toward the lower temperature zone for blends with g-PO against the pure polyamide (109). The extent of this shift increases with g-EPDM concentration in the blends. This finding witnesses a possibihty of increasing low temperature resistance of the blends if g-EPDM is introduced. 

The kinetics of formation and disintegration of micelles has been studied for about thirty years [106-130] mainly by means of special experimental methods, which have been proposed for investigation of fast chemical reaction in liquids [131]. Most of the experimental methods for micellar solutions study the relaxation of small perturbations of the aggregation equilibrium in the system. Small perturbations of the micellar concentration can be generated by either fast mixing of two solutions when one of them does not contain micelles (method of stopped flow [112]), or by a sudden shift of the equilibrium by instantaneous changes of the temperature (temperature jump method [108, 124, 129, 130]) or pressure (pressure jump method [1, 107, 116, 122, 126]). The shift of the equilibrium can be induced also by periodic compressions or expansions of a liquid element caused by ultrasound (methods of ultrasound spectrometry [109-111, 121, 125, 127]). All experimental techniques can be described by the term relaxation spectrometry [132] and are characterised by small deviations from equilibrium. Therefore, linearised equations can be used to describe various processes in the system. 

Relations (5.275), (5.276) can be used for the interpretation of experimental results obtained by surface relaxation spectrometry methods, for example, by the capillary wave method. 

Among various relaxation spectrometry methods of liquid surface layers the transverse capillary waves has been used most frequently for micellar solutions [96 - 101]. The shape of the concentration dependence of the wavelength is the same for all investigated cationic, anionic and nonionic surfactants and resembles the corresponding dependence of surface tension. Figure 16 shows as an example the experimental results for solutions of SDS [96]. 

This inequality agrees with the results of direct measurements of the formation and disintegration rate of micelles for solutions of DSN, DACh and CTACh [115]. To the best of our knowledge the micellisation kinetics in solutions of DPO has not been studied so far by relaxation spectrometry of the bulk phase. 

BAG Aniansson, SN Wall. In B Wyn-Jones, ed Chemical and Biological Applications of Relaxation Spectrometry. Dordrecht Reidel, 1975, p 223. 

E.A.G. Aniansson and S.N. Wall, Chemical and Biochemical Relaxation Spectrometry, E. Wyn-Jones (Ed.), Reidel, Dordrecht (1975). 

Various methods, including dilferential scanning calorimetry (DSC), dielectric relaxation spectrometry, and NMR, are known to be useful to determine molecular mobility of freeze-dried formulations [16,17]. The glass transition temperature (Tg) has been used as a measure of molecular mobility of lyophilized formulations, since it indicates the critical temperature of a-relaxation for amorphous polymer materials. Freeze-dried formulations containing polymer excipients can be considered to exhibit low molecular mobility without a-relaxation at temperatures below Tg. 

NMR is another useful means of measuring molecular mobility of freeze-dried formulations. The spin-lattice relaxation time in the laboratory frame (Ti) and the spin-spin relaxation time T2) of H, H, or have been used to represent the mobility of water and polymer molecules in freeze-dried cakes or aqueous polymer solutions [18-22]. In contract to DSC or dielectric relaxation spectrometry, NMR allows identification of the origin of molecular motion. Determining molecular mobility for each drug and excipient in a freeze-dried formulation is therefore possible when high-resolution solid-state NMR is used. 

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