Dynamic light scattering summarized

The use of photon correlation spectroscopy to study the dynamics of concentration fluctuations in polymer solutions and gels is now well established. In bulk polymers near the glass transition there will be slowly relaxing fluctuations in density and optical anisotropy which can also be studied by this technique. In this article we review the development of the field of photon correlation spectroscopy from bulk polymers. The theory of dynamic light scattering from pure liquids is presented and applied to polymers. The important experimented considerations involved in the collection and analysis of this type of data are discussed. Most of the article focuses on the dynamics of fluctuations near the glass transition in polymers. All the published work in this area is reviewed and the results are critically discussed. The current state of the field is summarized and many suggestions for further work are presented. 

The results are summarized in Table 2 and 3. Table 2 represents the results of the static and dynamic light scattering of the samples in aqueous suspension. The values of Rg, and My, have increased from the azofunctionalized microsphere to the PMMA-copolymer, i.e., the grafting reaction was successful. The p value of 0.9 shows that the particles are not aggregated after the polymerization which should result in much larger values of p. 

The average particle size as well as the particle size distribution of the prepared lattices was investigated under reaction state concentration using a novel dynamic light scattering method. Table 1 summarizes relevant data of the prepared products. Furthermore, the composition of the monomer feed as well as the composition of the polymer is given in Table 1. The polymer composition has been calculated from elemental analysis data. 

The theoretical basis and the most important applications of dynamic light scattering have been extensively treated in a number of books and a review article (1-9). For this reason only the most important principles will be summarized here and will be used... 

Several methods may be applied to determine the hydrodynamic thickness of adsorbed polymer layers of which viscosity, sedimentation coefficient (using an ultracentrifuge), and dynamic light scattering measurements are the most convenient. A less accurate method is from Z, potential measurements. These techniques are summarized below. 

In the Gaussian approximation (Eq. 4.12) the mean squared displacement is given by (r (t))=3/[2a(t)], and a2(t) is zero of course. In the light of the above results obtained by neutron scattering (summarized in Eq. 4.14), the values of the non-Gaussian parameter for this process should be very small. However, this result is in apparent contradiction to recent molecular dynamics (MD)... 

The light-scattering experiments described in Section VI used the mean intensity, scattered by a thin film, to find the mean square amphtude of the ripples. Now we summarize light-scattering experiments that deal with the dynamics of the ripples. 

This chapter has considered measurements of the dynamic structure factor S q, t) of polymer solutions. Here behaviors of the first cumulant, the polymer slow mode, and the high-frequency Rayleigh-Brillouin spectrum have been considered. Neutron spin-echo methods as supplements to light scattering spectroscopy were noted. Results on Ki and the Rayleigh-Brillouin spectrum are readily summarized. The discussion of the slow mode is considerably more extended, but leads to a comparison with modem models for glass formation. 

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