Quasielastic light scattering method

K. Ito, S. Qoi, N. Nishi, Y. Kimura, and R. Hayakawa. New measurement method of the autocorrelation function in the quasielastic light scattering method with the sinusoidal electric field. J. Chem. Phys., 100 (1993), 6098-6100. 

Dynamic surface tension has also been measured by quasielastic light scattering (QELS) from interfacial capillary waves [30]. It was shown that QELS gives the same result for the surface tension as the traditional Wilhelmy plate method down to the molecular area of 70 A. QELS has recently utilized in the study of adsorption dynamics of phospholipids on water-1,2-DCE, water-nitrobenzene and water-tetrachloromethane interfaces [31]. This technique is still in its infancy in liquid-liquid systems and its true power is to be shown in the near future. 

A series of monodisperse PMMA latexes was synthesized and characterized with respect to refractive index, percent solids, and solution density. The particle size of each latex was analyzed by several different instrumental methods. The methods used include DCP, SFFF, HDC, Quasielastic Light Scattering (QELS), TEM, and turbidity. 

Fig. 5 Comparison of various methods of particle size analysis Quasielastic light scattering, micro-Thhh, and hydrodynamic chromatography.

Comparison of transmission electron microscopy, quasielastic light scattering, hydrodynamic chromatography, and micro-TFFF, applied to the determination of the particle size distribution, demonstrated specific performances of these methods." Some of the results are shown in... 

Diblock copolymers were synthesised by two stepwise anionic polymerisation methods. One method produced diblock copolymer plus 30% of poly(2-vinylpyridine) homopolymer. The copolymers were dissolved in O.IM hydrochloric acid. When the pH was increased by the dropwise addition of 0.1 M sodium hydroxide, micelles with well-defined hydrodynamic diameters formed spontaneously at around pH 5. Further basification produced stable micelle structures and reacidification produced the mirror image of this titration curve. Blue swirls were observed when sodium hydroxide was added at pH4 or pH5. The micelle sizes were measured by quasielastic light scattering. It is shown that (1) it is possible to control micelUsation by pH and (2) formation of well-behaved micelles of variable hydrodynamic diameter is possible by titration of different ratios and different total polymer concentrations of poly(2-vinylpyridine/poly(2-vinylpyridine-block-PEO). Relevance to drug release systems that can remain intact and circulate for long periods within the vascular system is suggested. 17 refs. 

Freeze fracture electron micrographs were taken according to the method described previously [16], The mean diameter of the vesicles was measured by quasielastic light scattering (QLS) using Otsuka Electronics LPA 3000/3100. The calcein-entrapment efficiency of HCO-10 vesicles were determined as described [11]. 

As with all light scattering methods, the calculations necessary to analyze a bimodal particle size distribution from quasielastic light scattering data are very sensitive to noise in the data. Recently, however, Chu and coworkers (18) have reported a robust method for recovering bimodal distributions from their quasi-elastic spectra. 

Eq. (51) gives spectrum for the quasielastic light scattering for scatters undergoing translational diffusion, and is the equation used in obtaining difhision constants by this method. 

E. Miraldi, L. Trossi, P. T. Valabrega, Generalized method for nematic liquid crystal viscoelastic constant determination by quasielastic light scattering, II Nuovo Cimento 1980, 60, 165-186. 

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