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In this study, Fourier transform infrared, Raman and Brillouin spectroscopy have been used to study lipid phase behavior of hydrated as well as dried multilamellar l-α-phosphatidylcholine assemblies, in order to compare limitations and potentials of the different techniques. Dried lipid samples have been studied in the presence and absence of trehalose, which is known to affect the phase behavior of these systems. The methylene C-H stretching (2800–3000 cm−1) region in infrared (IR) and Raman spectra provided mutually consistent information on the rearrangement of lipid acyl chains occurring at the lipid melting temperature. IR spectra have a higher signal-to-noise ratio, thus permitting a more precise evaluation of the melting temperature. In the hydrated lipid samples, the C-H stretching region in the Raman spectra is less affected by the contribution of water compared with that in the IR spectra. Raman spectra are particularly suitable to simultaneously study both lipid and water contributions allowing to distinguish ice from non-frozen water below 0 °C. Brillouin light scattering was used to probe the collective dynamics, i.e. the propagation velocity and the attenuation of longitudinal acoustic modes in the lipid samples. Lipid phase transitions are evident from a change in the temperature behavior of the acoustic velocity. Moreover, a strong relaxation process with a characteristic time of 14 ps was observed in the sample dried without trehalose with a maximum in acoustic attenuation at about 45 °C, which likely reflects the rearrangement of acyl chains. Copyright © 2015 John Wiley & Sons, Ltd.

The elastic and elasto-optical properties of Rb1–x(NH4)x H2AsO4 mixed crystals were studied by Brillouin spectroscopy at room temperature. The measurements were made on single crystals obtained from the aqueous solution by slow evaporation. The behaviour of bulk phonons propagating in investigated crystals was studied for different polarisations of incident and scattered beam. The components of the tensors of elasto-optical and elastic properties of the crystals studied were determined. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we present the study of the acoustic phonons propagating in Er3+-doped KGd(WO4)2 single crystals by Brillouin spectroscopy. For the investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101] and [110] have been determined. Moreover, the values of the elastic constants: C22, C44 and C66 of Er3+-doped KGd(WO4)2 single crystals have been estimated. It was revealed that the presence of the Er3+-ions in KGd(WO4)2 crystals, for the used doping concentration 1 at% does not influence their elastic properties. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The elastic properties of the zinc tris (thiourea) sulphate crystal were studied by Brillouin spectroscopy in the range 80 – 300 K. The measurements were made on single crystals obtained by the isothermal method. The temperature dependences of the Brillouin shift were determined for the crystal in the principal directions and in a few mixed directions on a tandem type spectrometer. The results revealed anomalies in the bulk wave propagation rate and in a few elastic constants at about 138 K. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The analysis some of the acoustic phonons propagating in pure and Ho3+-doped KGd(WO4)2 single crystals in the GHz frequency range by Brillouin scattering method has been presented. For investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101], [101] and [110] have been determined. Moreover, the value of elastic constants C22, C44 and C66 of pure and Ho3+-doped KGd(WO4)2 single crystals have been estimated. It was revealed that the presence of the Ho3+-ions in KGd(WO4)2 crystals, for the used doping concentration 1 at% and 8 at%, does not influence their elastic properties. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Porous silicon films and multilayers were studied using Brillouin spectroscopy. Acoustic wave velocities and elastic constants were determined for films with porosity∼0.60 formed from p - , p + and n+ crystalline silicon. The velocities and elastic constants depend on the pore/crystallite geometry and morphology. Porous silicon multilayers were fabricated from (100) p + crystalline silicon. For a multilayer with 250 nm layer thickness and layer porosity sequence of 0.45/0.65/0.45/0.65/0.45, the Rayleigh surface phonon velocity was found to be 2850 m/s. The origin(s) of other peaks in the multilayer spectra are unknown but it is unlikely that they are surface modes because their shift(s) are independent of incident angle.

We report on the application of Brillouin spectroscopy as an approach to non-destructive optical characterization of the elastic constants of semiconductors with the wurtzite symmetry. Three different configurations were used to achieve a complete determination of the elastic stiffness constants of bulk AlN substrates grown by the Physical Vapor Transport (PVT) method. The scattering diagrams of these three configurations are presented showing the geometrical arrangements necessary to observe all the elastic stiffness constants for the partially nontransparent wurtzite type of the crystal structure. Because aluminum nitride (AlN) is a suitable material for the fabrication of light emitting devices, the characterization of its elastic constants was carried out very precisely to provide a reliable data which can be used for the determination of residual stress arising during the growth of AlN thin films or wide band gap semiconductor thin films on substrates of AlN. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The results of a study of KGd(WO4)2 single crystals by Brillouin scattering method are presented. The Brillouin spectra for the acoustic phonons propagating in the [100], [010], [001], [110] and [101] directions, taken in 90° and 180° scattering geometry at room temperature have been recorded. Using the Brillouin spectroscopy the refractive indices for some directions of KGd(WO4)2 crystals were determined. The refractive indices were also calculated for the same directions by the rotation transformation of the principal optical axes of the optical indicatrix to the crystallographic directions of KGd(WO4)2 crystals. Moreover, some anomalies of the acoustic phonons propagating connected with birefringence of KGd(WO4)2 crystals were discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Brillouin light scattering (BLS) from submicron-size patterned polyurethane (PU) films was found to display rich spectral features. Their identification allows the determination of the mechanical properties of the PU and the characterization of the periodicity and the coherence of the structure. A temperature-dependent study demonstrates that BLS is a sensitive tool to monitor changes of the mechanical properties and/or of the morphology.

The bismuth triborate (BiB3O6; BIBO) single crystal has been studied by Brillouin and Raman spectroscopy. Using Brillouin spectroscopy the propagation of the acoustic phonons in [100], [010], [001], [110] and [011] directions has been analyzed. The influence of birefringent and optical activity of BIBO crystal on some acoustic phonons has been discussed. The Raman spectra of the crystal in different scattering geometries have been recorded in the 50–1500 cm-1 spectral range at room temperature. The number and symmetry of Raman active modes was determined on the basis of site symmetry group analysis. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The paper reports results of Brillouin spectroscopy study performed on surface phonons in different crystallographic surfaces of crystals, in a wide temperature range but with particular emphasis on the temperatures covering the phase transition. The main aim of the study is to establish in which way the ferroelastic phase transition related to a strong soft bulk mode is reflected in the near-surface region of the ferroelastic crystals. Results of the Brillouin scattering of the surface phonons propagating in the ferroelastic crystal LiCsSO4 in the temperature range covering its phase transition are presented. Surface acoustic phonons in different planes and at various depths from the surface have been studied. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Directionally solidified mullite fibers have been grown by the laser-heated, float-zone method from starting materials with a nominal composition of 3Al 2 O 3 .2SiO 2 . The fibers used in this study have large single-crystal regions with composition 2.5Al 2 O 3 .SiO 2 and [001] fiber axis orientation. The complete elastic tensor of these samples has been determined by Brillouin spectroscopy at room temperature and elevated temperatures up to 1200°C. Isotropic moduli (bulk, shear, and Young's) have been calculated using the Voigt-Reuss-Hill averaging scheme. The room-temperature values obtained are K VRH = 173.5 ± 6.9 GPa, G VRH = 88.0 ± 3.5 GPa, E VRH = 225.9 ± 9.0 GPa. All moduli show gradual, linear decreases with temperature. The temperature derivatives obtained for the equivalent, isotropic moduli are dK VRH /dT = -17.5 ± 2.5 MPa/°C, dG VRH /dT = -8.8 ± 1.4 MPa/°C, dE VRH /dT = -22.6 ± 2.8 MPa/°C. Substantial differences between bulk properties calculated from the single-crystal measurements in this study and the properties reported in the literature for polycrystalline sintered mullite are identified, indicating the importance of factors such as microstructure, intergranular phases, and composition to the elasticity of mullite ceramics.

Using Brillouin spectroscopy (BS), the tensor of the elastic constants of oriented poly(ethylene terephthalate) was determined for a variety of morphologies obtained by different uniaxial drawing procedures. The extreme values of the moduli along the drawing direction at frequencies of a few gigahertz were C33 = 40 GPa and C44 = 1.8 GPa. As a result of the invariants of the single-phase aggregate model, the oriented state is dominated by the Reuss average even at extreme draw ratios and subsequent to a deformation-induced crystallization. This is documented in both the BS orientation parameter and the BS mode numbers in comparison with birefringence. Additional spectral lines observed at draw ratios larger than 6 are discussed in relation to the formation of nanostructured phases. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1201–1213, 2002

The confocal Brillouin spectroscopy is an innovative measurement method that allows the non-invasive determination of the rheological properties of materials. Its application in ophthalmology can offer the possibility to determine in-vivo the biomechanical properties of transparent biological tissue such as the crystalline lens. This seems to be a promising approach concerning current presbyopia research. Due to the spatially resolved detection of the viscoelastic lens properties, a better understanding of the natural aging process of the lens and the influences of different lens opacities on the stiffness is expected. From the obtained spectral data the relative protein levels, the relative refractive index profile and the relative density profile within the lens tissue can be derived. A measurement set-up for confocal Brillouin microscopy based on spectral analysis of spontaneous Brillouin scattering signals by using a high-resolution dispersive device is presented. In-vitro and in-vivo test results on native and artificial lenses are presented and evaluated concerning their rheological significance.

The reaction of 1,4-butanediol diglycidyl ether (EP) with cis-1,2-cyclohex-anedicarboxylic anhydride (CH) and triethylamine (TEA) as an initiator was studied with temperature scanning Brillouin spectroscopy (TSBS) and differential scanning calorimetry (DSC). The evolution of the reaction process (liquid-gel-solid) was investigated as a function of the epoxy molar fraction (x EP ), for sample compositions varying from an epoxy excess to an anhydride excess. The dependence of the final conversion factors αr DSC and αr TSBS and the kinetic parameters E DSC and E TSBS on x EP is presented. A comparison of the experimental gelation point (Pgel) behavior and the expected theoretical one, described by the Flory theory, is also reported.

Thin amorphous films of PTC and PLZT of 1-3 μm thickness were produced by rf-sputtering at ambient temperature. Different grain sizes between the subnanometer and the micrometer region could be prepared by a subsequent annealing process. The increasing size of the crystallites was characterised by profile analysis of x-ray powder diffraction spectra. It is expected that the small grain size of compact nanocrystalline materials will have drastic influences on their elastic properties. High resolution Brillouin spectroscopy was used to probe the hypersonic properties of the two materials at ambient temperature. For the PLZT samples the elastic modulus c 11 shows the expected increase at the transition from the amorphous to the nanocrystalline state. On the contrary the PTC samples exhibit a surprising elastic instability in the same region.

We present a new method to interpret data obtained by Brillouin-scattering from oriented networks. Because in rubberlike samples the transverse sound waves are normally not observable, it is not possible to extract the complete set of elastic constants. We will show that by combining a model of the orientation process with the lattice-model from Kondo and Igarashi, force constants can be determined from the sound velocities. These force constants can be discussed in terms of molecular conformations and interactions. The anisotropic hypersound velocity was measured in polyurethane- and polysiloxane networks. With the help of the combined orientation-lattice-model evaluation, different kinds of forces can be distinguished. By comparing the force constants with Raman- or infrared spectroscopic data, information about the conformation of the polymer chains can be determined. The effective force constants of the segments are an order of magnitude lower than that of the polymer main chains and the ratio of force constants along and between the segments lies between 1 : 1 to 5 : 1. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1661–1676, 1997

The aim of this article is to investigate the effect of nanoparticle clustering on the mobility of nanoparticles in nanocom- posites, using spectroscopic methods (Brillouin and Raman). Special attention is paid to the effect of particle clustering on photocur- ing kinetics. The model system was poly(2-hydroxyethyl acrylate) filled with fumed nanosilica in concentration range encompassing the percolation threshold. Results obtained from Brillouin spectroscopy show substantial changes in the sound velocity and the attenuation coefficient with increasing filler content. The damping of acoustic waves reaches the maximum at the percolation thresh- old (� 15 wt %), which is related to changes in the mechanism of acoustic wave propagation. The formation of the cocontinuous silica phase strongly affects the curing kinetics of the monomer/silica system: the polymerization rate is the highest at a silica content corresponding to the percolation threshold. These results correlate well with the results of AFM surface roughness analysis. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013, 000, 39895.

Slowly relaxing longitudinal density fluctuations in an optically perfect sample of bulk poly(n-hexyl methacrylate) (PHMA) have been studied by photon correlation spectroscopy in the temperature range 10-36°C. The glass transition temperature for this sample was in the temperature range 10-36°C. The glass transition temperature for this sample was measured to be T g = -3°C by differential scanning calorimetry. The optical purity of the sample was verified by Rayleigh Brillouin spectroscopy and the Landau Placzek ratio was observed to be 2.3 at 25°C. Light-scattering relaxation functions were obtained over the time range 10 6 -l s. The shape of the relaxation functions broadened as the temperature was lowered towards the glass transition. Quantitative analysis of the results was carried out using the Kohlrausch-Williams-Watts (KWW) function to obtain average relaxation times , and width parameters, β. The width parameter decreased from 0.43 to 0.21 over the temperature interval, as suggested by visual inspection. Average relaxation times shifted with temperature in a manner consistent with previous mechanical studies of the primary glass-rubber relaxation in PHMA. The relaxation functions were also analyzed in terms of a distribution of relaxation rates, G(T). The calculated distributions were unimodal at all temperatures. The average relaxation times obtained from G(T) were in agreement with the KWW analysis, and the shape of the distribution broadened as the sample was cooled. The rate at which G(T) displayed a maximum correlated well with the corresponding frequency of maximum dielectric loss for PHMA. The temperature dependence of these two quantities could be reproduced with an Arrhenius activation energy of 21 Kcal/mol. A consistent picture of the molecular dynamics of PHMA near the glass transition requires a strong secondary relaxation process with a different temperature dependence from the primary glass-rubber relaxation. The present results suggest that the behavior of PHMA is similar to the other poly(alkyl methacrylates).

The network formation process of the triethylamine-initiated reaction of 1,4-butanediol diglycidyl ether with cis-1,2-cyclohexanedicarboxylic anhydride has been investigated by conventional differential scanning calorimetry and temperature scanning Brillouin light scattering as a new experimental method for the estimation of the reaction's conversion factor. The time-temperature evolution of the observed quantities (reaction enthalpy in the calorimetric measurements and hypersound velocity in the light scattering) reflects in both sets of experimental data, but results in different kinetic parameters obtained by the assumption of an Arrhenius behavior. These differences are ascribed to the relation of the observed properties with respect to the evolution of the reaction. The enthalpy production of the system observed in the calorimetric experiment is shown to be connected directly to the chemical reaction, whereas the change in the hypersound velocity measured by the light scattering method is sensitive to the solidification of the system. © 1995 John Wiley & Sons, Inc.

The room temperature phase of the physical/chemical vapor-deposited statistical co-oligomer VDF/TrFE(70/30) has been characterized by different experimental methods such as small-angle x-ray scattering, wide-angle x-ray diffraction, size-exclusion chromatography, infrared absorption and optical refractometry. The characterization of the elastic properties was carried out using high-performance Brillouin spectroscopy in connection with special scattering geometries. The co-oligomer VDF/TrFE(70/30) was obtained by cracking the parent statistical copolymer and subsequently vapor depositing the shortened chains on highly oriented PTFE substrates (PIA-technique). The room temperature phase of the resulting oriented waxy crystal mats of VDF/TrFE(70/30) is predominantly ferroelectric. The physical properties are very different to those of similarly PIA-prepared n-alkanes, perfluoroalkanes, and blockfluoroalkanes. The microstructure of VDF/TrFE(70/30) is interpreted in terms of partially crystalline nano-sized structures giving rise to a marked freezing process below room temperature. © 1995 John wiley & Sons, Inc.

The elastic constants of hydrothermally grown single crystals of GaAsO4 are determined by Brillouin spectroscopy.

Brillouin scattering measurements have been carried out at room temperature on the CBr 4 clathrate of hexakis-(phenylthio)benzene. This material crystallizes in the R3 space group (trigonal system), with a host:guest mole ratio of 1:2. The value of all seven adiabatic elastic constants were determined. The material is elastically more anisotropic than the previously investigated ethanol-Dianin's compound clathrate which has the same space group, yet the bulk modulus and the linear compressibilities of these materials are similar

We present Rayleigh-Brillouin light scattering data of highly syndiotactic poly(n-butyl methacrylate) [PBMA] whose glass transition temperature as measured by DSC is 55°C. The Brillouin peak shifts, Brillouin peak widths, and Landau-Placzek ratios from −15 to 130°C are reported. The Brillouin peak widths decrease continuously through the glass transition region. This indicates a continual decrease in the strength of processes whose relaxation times are about 10−10 s with decreasing temperature even as the system becomes glassy. The Landau-Placzek ratio above the glass transition is about 3, indicating the high optical purity of our sample. This low Landau-Placzek ratio arises from the sample's homogeneous stereochemistry. Some of the anomalous behavior observed around 40–50°C in previous PBMA studies is explained in terms of syndiotactic regions within a largely atactic sample.

The low-frequency acoustic vibrational modes of solid poly(ethylene) (PE) oriented by stretching and hydrostatic extrusion are studied with Brillouin spectroscopy. The experimental results evidence a damping of the longitudinal acoustic mode propagating in the direction parallel to the orientation axis of the samples. The results are discussed in terms of the theoretically derived acoustic dispersion relations for the PE crystal.

The topochemical polymerization of the substituted diacetylene, 2,4-hexadiynylene bis(p-toluenesulfonate) (1), has been followed by X-ray crystallography and by determination of the elastic constants of polymerizing crystals. For the first time the crystal structure of a polymerizable diacetylene monomer has been solved and the coordinates of all atoms prior and after the reaction have been determined. The length of the growing polymer chains and their distribution in the monomer matrix can be determined by the evaluation of the Brillouin spectra in terms of a model which considers the polymerizing crystal as a composite material of high-modulus rod-like macromolecules dispersed in the low-modulus matrix of the residual monomer.

The technique of high resolution Brillouin spectroscopy is used to determine the adiabatic elastic constants of oriented single crystals of carbon tetraiodide for temperatures near and at the triple point. The values obtained at 280 K are c11 = 2.4 (67), c11 = 2.1 (69), and c12 = 0.28 (71) (in units of 109Nm−2)with an estimated uncertainty of ±2%. Die Technik der hochauflosenden Brillouin-Spektroskopie wird benutzt, um die adiabatischen elastischen Konstanten von orientierten Einkristallen von Kohlenstofftetrajodid fur Temperaturen am Tripelpunkt und in dessen Nahe zu bestimmen. Die bei 280 K erhaltenen Werte sind c11= 2,4 (67), c12= 2,1 (69) und c44= 0,28 (71) (in Einheiten von 109Nm−2) mit einer geschitzteii Unsicherheit von ±2%.

Some physical investigations of segmented block copolymers of uniform chain length and defined structure and their constituents are described. Special attention was payed to the thermal behaviour of these new substances with respect 1. to the phase transformations in the solid and liquid state and 2. to the thermal stability of the materials. Several of these oligomers show phase transitions in the solid state. In some instances, the morphology of the solid material depends strongly on the sample history. The influence of the crystallization conditions is discussed. For the special case of esters of 4,4′-isopropylidenediphenol (bisphenol A) with isophthalic acid detailed investigations by dielectric and Brillouin spectroscopy of the glass-forming process are presented.

We have used Brillouin spectroscopy to study the velocities and attenuation of acoustic phonons in wet-spun films of Na-DNA and Li-DNA as a function of the degree of hydration at room temperature. Our data for the longitudinal acoustic (LA) phonon velocity vs water content display several interesting features and reveal effects that we can model at the atomic level as interhelical bond softening and relaxation of the hydration shell. The model for interhelical softening makes use of other physical parameters of these films, which we have determined by gravimetric, x-ray, and optical microscopy studies. We extract intrinsic elastic constants for hydrated Na-DNA molecules of c11 ≃ 8.0 × 1010 dynes/cm2 and c33 ≃ 5.7 × 1010 dynes/cm2, which corresponds to a Young's modulus, E ≃ 1.1 × 1010 dynes/cm2 (with Poisson's ratio, σ = 0.44). The negative velocity anisotropy of the LA phonons indicates that neighboring DNA molecules are held together by strong interhelical bonds in the solid state. The LA phonon attenuation data can be understood by the relaxational model in which the acoustic phonon is coupled to a relaxation mode of the water molecules. Na-DNA undergoes the A to B phase transition at a relative humidity (rh) of 92% while Li-DNA (which remains in the B form in this range) decrystallizes at an rh of 84%. We find that our Brillouin results for Na- and Li-DNA are remarkably similar, indicating that the A to B phase transition does not play an important role in determining the acoustic properties of these two types of DNA.

Automation techniques based upon the latest microprocessor computer technology are described in general terms for applications in light scattering spectroscopy. Two practical systems are described in detail. The first system operates a Raman spectrometer and handles the data collection automatically, storing the spectrum in digital form on disc and providing visual displays simultaneously. The second controls the alignment and scanning of a multi-pass Fabry-Perot spectrometer as well as data acquisition. Finally, prospects for future systems are reviewed.

Brillouin spectroscopy was evaluated as an experimental method for measuring the molecular weights of macromolecules. This evaluation included an examination of instrumental parameters, sample preparation, and spectral analysis. The Brillouin peaks were found to be independant of solute concentration for dilute solutions, in accordance with the assumptions of Miller's approximate theory. This theory was used to calculate molecular weights of five standard polystyrene samples. These values compared well with molecular weights derived from regular photometric light scattering and viscosity measurements.

The technique of high resolution Brillouin spectroscopy has been used to determine the adiabatic elastic constants of oriented single crystals of β‐carbon monoxide at temperatures near the triple point. The values obtained at 67.7 K were c11=1.9(01), c12=1.1(46), c13=0.9(51), c33=2.0(95) and c44=0.35(5) (in units of 109 Nm−2) with an estimated uncertainty of ±2%. The similarities to β‐nitrogen results are striking; nevertheless, significant differences are noted.

The technique of high resolution Brillouin spectroscopy has been used to determine the adiabatic elastic constants of oriented single crystals of plastic cyclohexane for temperatures near and at the triple point. The values obtained at 279.2 K were c11 =2.8(57), c12=2.4(72), and c44=0.35(8) (in units of 109 N m−2) with an estimated uncertainty of ±2%. There is evidence for the occurrence of considerable dispersion in the solid, especially near the triple point.