Brillouin scattering from polymer

Brillouin scattering measures the velocity and attenuation of hypersonic thermal acoustic phonons. A theory of Brillouin scattering from polymer blends is presented and illustrated qualitatively by several examples. The study of blend compatibility is illustrated for the system PMMA-PVFS. The detection of inhomogeneous additives is shown for commercial PVC film and cellulose acetate, and simultaneous measurements on separated phases are presented for Mylar film. The main purpose of the paper is to stimulate further work in a potentially promising field. 

Patterson, G. D., Latham, J. P., Brillouin Scattering from Polymers, ... 

Brillouin scattering from the nematic (racemic) lyotropic polymer poly-y-benzyl glutamate (PBG) shows a significant anisotropy in both the sound velocity (22%) and the Brillouin linewidth (40%) in the solutions [22], when measurements are made at different angles with respect to the nematic director. Figure 4 shows typical Brillouin spectra of PBG as a function of scattering angle. This work indicates the importance of elastic relaxations due to concentration fluctuations in these nematic polymeric materials. 

FIGURE 60.8. Sound velocity of the longitudinal polarized phonon measured parallel (filled squares) and perpendicular (empty circles) to the draw direction measured by Brillouin scattering. The samples are polydiethylsiloxanes with Mn = 45,000 and 43,000 labeled as PDES-45 and PDES-3, respectively [15]. Reprinted from S.H. Anders, H.H. Krbecek, and M. Pietralla, J. Polym. Sci., Polym. Phys. Ed. 35, 1661-1676 (1997). Copyright 1997, with permission of Wiley-VCH. 

Since then, attempts have been made to improve and modify Debye s (1959) theory of critical opalescence. Vrij and van den Esker (1972) have accounted for the influence of local concentration gradients on the entropy term of the friee energy F in their consideration of light scattering from moderately-concentrated polymer solutions in terms of Silberberg s (1952) model (recall that Debye allowed for their influence on the entropy term only). To calculate the scattering intensity 7, they used the Fourier transformation of the concentration fluctuations and Brillouin (1922)-Debye s (1959) formalism... 

Besides pcs, other light scattering techniques including Brillouin scattering and Fabry-Perot interferometry described in previous sections have been applied to probe the dynamics of polymers at higher frequencies than the more conventional techniques. Interpretations of the results from these techniques are still subjects of controversy and are not discussed here. 

Krbecek, H., Kruger, J.K. and Pietralla, M. (1993) Poisson ratios and upper bounds of intrinsic birefringence from brillouin scattering of oriented polymers. J. Polym. Sci. Phys. Ed., 31, 1477. 

A liquid or gas or amorphous polymer can be considered a giant system of interacting particles which possess collective vibrational modes characteristic of the fluid as a whole. It is from these motions that Brillouin scattering may be said to arise. Thus the above treatment can be considered to hold for Brillouin scattering as well if is considered a normal... 

Fig. 14. Schematic views of (a) manifestation of transitions in a DMA spectrum, and (b) frequency dependencies of transition temperatures in polymers, measured by various techniques I, DSC, mechanical relaxation, radiothermoluminescence, thermostimulated depolarization II, mechanical and dielectric relaxation III, dielectric relaxation, NMR IV, ESR (probe method), Mandelstam-Brillouin scattering, acoustic measurements (From Ref 140),...

The neutron experiments have been made at Laboratoire Leon Brillouin on the spectrometer PACE. The range of scattering vector, 10 A < q < 10 A, is chosen to probe the inner structure of the layers, ctftg > > 1. For both systems, the partial structure factors of the polymer are extracted from the difference between the signal of the polymer-coated solid and that of the bare solid, observed at three different contrasts. 

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