Light scattering by transverse waves in supercooled liquids and application to metatoluidine

Abstract

We discuss the hydrodynamic equations which describe the shear dynamics of a liquid composed of anisotropic molecules, both in its normal and its supercooled phases. We use these equations to analyze 90 • depolarized light scattering experiments performed in the supercooled phase of a glass forming liquid, metatoluidine, and show that the information extracted from this analysis is consistent with independent shear viscosity measurements performed on that liquid in the same temperature range. PACS. 66.20.+d Viscosity of liquids; diffusive momentum transport -78.35.+c Brillouin and Rayleigh scattering; other light scattering -64.70.Pf Glass transitions

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

“…One of a very powerful tool in studies of glasses is Brillouin spectroscopy since it has been shown to give valuable information on the dynamical properties of glass-forming materials in the gigahertz region. [1][2][3][4][5][6][7][8] The relaxational processes have been extensively studied for glass formers without directional bonds, which show a similar high increase of viscosity upon supercooling and are called fragile systems. 3,6,7 The dynamics of these fragile systems is relatively well understood on the basis of mode coupling theory.…”

“…[1][2][3][4][5][6][7][8] The relaxational processes have been extensively studied for glass formers without directional bonds, which show a similar high increase of viscosity upon supercooling and are called fragile systems. 3,6,7 The dynamics of these fragile systems is relatively well understood on the basis of mode coupling theory. 6,9 On the other hand, in the presence of directional bonds the temperature variation of viscosity is weaker, and the dynamics of these so-called strong and intermediate glass formers is still not well understood.…”

“…Studies of both LA and TA modes are, however, of great interests since they provide important data on structural changes that occur in glasses, temperature dependence of viscosity, and the elastic properties of materials. 3,7,8,11 Two other powerful techniques, frequently employed in the studies of glass-forming materials, are Raman spectroscopy and heat capacity measurements. The first technique gives information about short-range structure of glasses and allows studying the so-called "Boson peak."…”

α-Scale decoupling of the mechanical relaxation and diverging shear wave propagation length scale in triphenylphosphite

“…Acoustic transducer [10,11], Impulsive Stimulated Scattering (ISS) [12][13][14] and highfrequency forced Brillouin Scattering [15] techniques can continuously cover the longitudinal spectrum up to the * kanelson@mit.edu mid-GHz regime. However, broadband shear wave generation is more accessible experimentally at lower frequencies and exhibits a gap in the range from the ∼ 10 MHz limit of transducer methods [10,11] to the low GHz frequencies probed by depolarized (VH) Brillouin Scattering [16][17][18][19][20][21]. The vast majority of depolarized Brillouin Scattering studies are conducted in a single scattering geometry, permitting observation of only one acoustic wavevector.…”

Shape Persistence in Polymers and Supramolecular Assemblies

“…The observed differentiation can be attributed to non-random spatial orientation correlations due to rotation-translation coupling proposed for small molecules. [52][53][54][55][56] For semi-flexible polymers, however, the effect is strong and the dynamics are slow that renders the finding unique. A further advantage is the observation of the effect at equilibrium without macroscopic flow.…”