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New details on the structure of β-casein adsorbed layers, at the air–water interface, have been obtained using X-ray and neutron reflectivity. The experimental data are fitted well by a power law model and the results discussed in terms of the distribution of amino-acid sequences between trains, loops and tails. This distribution seems to be consistent with statistical theories established for flexible polymers. The trains are present in close proximity to the surface as a dense layer 8–9 A thick. At low surface coverage, the tail effect is negligible and the adsorbed layer is composed of nearly 60% amino-acid sequences in trains and the remaining in loops. When the bulk concentration is increased, a substantial part of the amino-acid residues has to be accommodated in loops and long tails; the adsorbed layer becomes more extended (80–100 A). A striking feature is observed for a high bulk concentration (10−1 wt.%): trains are forced to eject out of the interface.

On utilise la reflectivite des rayons X pour etudier l'influence de l'etalement de monocouches d'acides gras sur la structure superficielle du mercure liquide. Pour des pressions de surface telles que l'aire disponible est voisine de 25 A 2 / molecule, les molecules d'acides pentadecanoique, stearique, eicosanoique ou behenique s'orientent perpendiculairement a la surface. La structuration superficielle qui existe a la surface du mercure nu ne semble etre sensiblement modifiee lorsqu'une monocouche est etalee.

Langmuir-Blodgett films of mesomorphic side-chain poly(methacrylates) are investigated from the point of view of their phase change versus temperature via X-ray and neutron reflectivity together with atomic force microscopy measurements. Upon heating, «thick» films undergo an irreversible transition toward the wellknown smectic Ar lamellar phase. In contrast, a bilayer deposited onto a solid substrate appears to be very stable upon annealing. Such a behavior is believed to induce an epitaxial mechanism when cooling «thick» films from the isotropic melt phase

Langmuir-Blodgett films of mesomorphic side-chain polymethacrylates are investigated from the point of view of their phase change versus temperature via X-ray and neutron reflectivity. Upon heating, “thick” films undergo an irreversible transition towards the well known smectic Al lamellar phase. In contrast a bilayer deposited onto a solid substrate appears to be very stable upon annealing. Such a behaviour is believed to induce an epitaxial mechanism when cooling “thick” Rims from the isotropic melt phase.

The adsorption of poly(dimethylsiloxane) to the in surface from solution in bromoheptane (good solvent) and bromocyclohexane (T θ =29 o C) has been studied. The sensitivity of the XEWIF technique to the first ∼40 A of the surface region allows the determination of important qualitative features of the absorbed concentration profiles. In a good solvent, the region of the profile nearest to the surface (∼40 A) is roughly independent of molecular weight in dilute solution. For near-θ conditions, the adsodrbed amount in dilute solution was found to be ∼4 times larger than in good solvent, with the profile decaying much more slowly with depth than in good solvent

The synthesis and the characterization (gel permeation chromatography, FAB mass spectrometry, NMR spectroscopy) of a bisphthalocyanine derivative substituted with twelve (2-ethylhexyl)oxy side chains are described. This compound and the corresponding copper complex are shown to form mesophases, probably related to a nematic order. Electron spin resonance (ESR) studies demonstrate a highly anisotropic rotation of the molecule in solution; in the mesophase, both intramolecular antiferromagnetic and intermolecular ferromagnetic couplings have been observed

The structure of water absorbed in polyHEMA is studied by X-ray diffraction in the vitreous state at 77 K as well as in the liquid state at room temperature. Molecular packing at the level of the first neighbors is found similar to that in bulk water but a distortion is observed at the level of the second neighbors which is attributed to the bending of the H bonds. From the widths of the Bragg peaks of the crystalline ices from the small-angle neutron scattering results, we deduce that the pore size and the interpore distance in the swollen polyHEMA are smaller than 30 A.

In the liquid state, water molecules tend to be surrounded tetrahedrally by four other molecules. This tendency gives rise to a three-dimensional open network which is a feature of most of the solid phases: in addition to the many polymorphic crystalline forms presently known, there exist glassy and amorphous ices with unique hydrogen-bonded structures. In this paper, we briefly review the structural properties of the crystalline and non-crystalline phases including the more recent data quoted in the literature.

Etude par DSC, diffraction RX et microscopie polarisee du polyphosphorene [N=PR 2 ] n (R=OCH 2 CH 2 OPh-N=N-Ph-Bu) obtenu a partir du poly(dichlorophosphazene). Le polymorphisme cristal-smectique C-smectique A-liquide isotrope est observe. Des fibres orientees avec une maille cristalline ortho-rhombique sont obtenues par refroidissement lent de l'etat cristallin liquide

The specular reflectivity of x-rays at sufficiently small grazing angles is absorption-coefficient-dependent so that the EXAFS technique can be used to probe the surface. This method allows in situ measurements. Applications to the study of passive films on nickel and nickel-molybdenum alloy electrodes are presented. In both cases, the passive films is found to be composed of NiO entities probably ordered perpendicularly to the electrode. Molybdenum enrichment in the surface layer is confirmed by an increase of the Mo k edge signal.

L’intensite diffractee par le toluene liquide a ete mesuree a differentes temperatures comprises entre 153 et 293 K (point de fusion normal du toluene : 178 K); une etude a egalement ete effectuee a 77 K sur les phases solides non cristallines, vitreuse et amorphe, obtenues respectivement en refroidissant le liquide en dessous de la temperature de la transition vitreuse et en deposant la vapeur de toluene sur un support maintenu a basse temperature. Les mesures effectuees dans l'intervalle du vecteur de diffusion compris entre 0,4 et 13,0 A-1 montrent que, dans le domaine de temperature etudie, l'intensite resultant des interactions entre les atomes appartenant a des molecules distinctes devient negligeable au-dela de 6 A-1 et qu’il n’existe pas de difference sensible entre les facteurs de structure des phases vitreuse et amorphe. Les fonctions de distribution radiale, obtenues par inversion de Fourier des intensites experimentales, ont ete calculees dans l’approximation des atomes independants et en admettant une sphericite effective des molecules de toluene. L'ordre moleculaire dans les phases non-ordonnees est compare a l’ordre existant dans le toluene cristallise.

The crystal structure of the metastable β-phase of toluene is determined from single crystal X-ray diffraction data using a Monte-Carlo method coupled to a constrained leastsquares refinement. At 105 K β-toluene is orthorhombic (space group Pbcn ; a = 13.85 A, b = 11.42 A, c = 7.39 A ; Z = 8). Relations between the packing of the molecules in this modification and in the normal crystalline α-phase are discussed.

From measurement of the angular dependence of X-ray reflectivity on mercury and gallium it is concluded that the density variation in the liquid-vapor interface near the triple point cannot be represented by a step-like profile. Our results suggest non-monotonic profiles.

An automatic θ-θ diffractometer has been built in which X-ray source and detector rotate about a fixed horizontal specimen, in such way that measurements can be carried at equally spaced values of the scattering vector modulus. This especially designed diffractometer for the study of liquids and glassy materials, is provided with a cryostat allowing diffraction measurements down to very low temperatures. Some results are reported concerning liquid gallium at 323 and 203 K., On a réalisé un diffractomètre automatique θ-θ où tube à rayons X et compteur se déplacent autour d'un échantillon fixe, horizontal, de façon à faire des mesures sensiblement équiréparties dans l'espace réciproque. Ce diffractomètre, particulièrement adapté à l'étude des liquides et des substances vitrifiables, a été équipé d'un cryostat qui permet d'effectuer des mesures de diffraction jusqu'à très basse température. Quelques résultats concernant le gallium liquide à 323 et 203 K sont donnés., Bizid Abdelmalek, Bosio Louis, Cortès Robert, Defrain André. Diffractomètre θ-θ à axe horizontal pour étude aux rayons X jusqu'à très basse température. In: Bulletin de la Société française de Minéralogie et de Cristallographie, volume 100, 1, 1977. pp. 9-14.

We report neutron-scattering measurements on highly supercooled liquid gallium droplets showing a vanishing quasi-elastic frequency width as the temperature is reduced. The width tends towards zero at a temperature within 1 standard deviation of the value ${T}_{L}=150\ifmmode\pm\else\textpm\fi{}1$ K at which gallium is always observed to become crystalline. This suggests the interpretation of ${T}_{L}$ as a metastability limit, below which the liquid state becomes unstable with respect to infinitesimal fluctuations.

The structure of liquid mercury has been studied with both CuKα and MoKα radiation using a theta–theta diffractometer with monochromator in the diffracted beam. Special attention has been paid to the temperature dependence of the liquid structure and the use of small droplets of about 5 μm diameter actually allowed measurements on supercooled liquid down to 60 K below the normal melting point. No significant variation in the first coordination number is observed over the temperature range studied, the change in the shape and the height of the first peak of the structure factor being probably due to some long range correlation increase when the temperature is lowered. A structure model based on a relaxed lattice is found to fit satisfactorily the experimental pair correlation function for liquid mercury.

Amorphous films of some μm in thickness, prepared by low temperature condensation in an ultra-high vacuum onto liquid helium cooled substrates, have been studied in situ by using an X-ray diffractometer operating in a symmetrical reflection mode. The structure factor of gallium has been obtained over the wavevector range 1.3 to 16.1 A − by means of two wavelengths, Cr Kα and Mo Kα , monochromatized by balanced filters. The average number of nearest neighbours deduced from the well-resolved first maximum in the radial distribution function is equal to 9.3 atoms. The results are compared to those previously found by electron diffraction measurements on thin films and also to the structure of supercooled liquid.

Data reduction for EXAFS experiments on Fe80B20 and Fe80P20 metallic glasses has been achieved only after the iron phase shifts have been adjusted from pure α-iron spectra and the asymmetric nearest neighbor peak shape has been modelled. A comparison is made with the results of X-ray diffraction studies.

A simple spectrometer using a conventional X-ray generator has been constructed for ReflEXAFS measurements at glancing angle. The X-ray source is a sealed X-ray tube with a parabolic mirror. A monochromator with two flat LiF crystals is used. The energy resolution amounts to 8.5 eV at 8 keV. A proportional counter monitors the incident X-ray intensity and a NaI scintillation detector measures the intensity of the reflected beam. This system is free from fluctuations of the incident X-ray intensity and harmonics can be rejected with the energy discrimination. The range of energy is 7 to 18 keV. The ReflEXAFS spectra related to the surface of a nickel sample and a thermally oxided nickel sample are presented.

Quite recently, it has been found that X-ray absorption spectroscopy may be used as a probe for passive films. We measured the reflectivity vs. the incident energy from bulk samples and now report the preliminary results obtained from in situ measurements on passivated nickel.

X‐ray diffraction measurements up to momentum transfer q=16 A−1 were performed at atmospheric pressure on both the high‐density form of amorphous ice obtained by pressurization of crystalline ice Ih at 77 K up to 2 GPa and the low‐density form obtained by further heating. These two amorphous phases exhibit significant differences at the level of the second‐ and third‐nearest neighbors which involve a decrease of the O–O–O angle on compression at high pressure. Moreover, it is found that the low‐density form is quite similar to that obtained by vapor deposition on cooled substrates at 77 K.

Within the liquid crystalline domain, dihydroxysilicon(IV) octakis(dodecyloxymethyl) phthalocyanine is polycondensed to give a distribution of polysiloxanes. These latter form a mesophase with lamellar order. For the first time polycondensation has been carried out in a columnar mesophase and a new type of oligomeric mesogen has been obtained. The term spinal columnar liquid crystal is proposed to designate such a mesophase.

The crystal and molecular structures of syndiotactic 2,4,6,8-tetraphenylnonane have been determined by direct methods and refinement from X-ray diffraction data. The unit cell is quadratic (space group I 4 1 /g) with, at room temperature, g  13.740, c  27.20 A, V = 5135.7 A, Z = 8 and contains one molecule in the asymmetric unit; the final weighted residual factor is r = 0.065 for 1541 observed reflexions. It is found that the aliphatic chain exhibits a gauche-gauche conformation in the middle of the chain.

Les resultats d'analyse enthalpique differentielle effectuee sur des echangillons de cyclohexane de volume voisin de 1 µm 3 avaient ete interpretes en admettant l'apparition, au cours du refroidissement, de deux phases solides metastables — respectivement β et δ — distinctes des formes stables I (c.f.c.) et II (monoclinique). Des diagrammes de poudre, obtenus par diffraction des rayons X, confirment l'existence de ces phases et montrent que la variete 6 est identique a la phase que l'on peut obtenir par trempe rapide d'un echantillon liquide de quelques mm 3 .

Le tetrachlorure de carbone possede, a la pression atmospherique, trois varietes allotropiques : cubique (Ia , rhomboedrique (Ib ) et monoclinique (II). Les retards accompagnants les transitions de phases dependent fortement des dimensions des echantillons et les diagrammes de poudre realises sur des echantillons divises en fines gouttelettes montrent en particulier qu’il existe une enantiotropie entre les varietes Ia et II a une temperature ou chacune de ces phases est metastable.

A four-block mesogen composed of three chemically different moieties is synthesized. Its mesomorphic properties are characterized by optical microscopy, differential thermal analysis and X-ray diffraction at small angles, demonstrating a smectic C structure between 92°C and 111°C. The notion of a polyphile is defined and the expected peculiarities of such compounds are emphasized.

A copper complex of a phthalocyanine substituted with four benzo-15-crown-5 1,Cu and the corresponding dihydrogeno-derivative 1,H2 were synthesized. X-ray determinations at small angles permitted us to characterize two types of condensed phases. Solid phases with orthorhombic structure were found for 1,H2 and for 1,Cu (a=20.5, b= 18, c=4.2 A). In these forms, two-dimensional rectangular arrays of substituted phthalocyanines lead to corrugated planes. Phthalocyanine moieties are superposed in an eclipsed conformation and the crown-ether macrocycles form channels. Metastable mesophases could also be characterized by X-ray diffraction. In this case, only two broad lines at 20.8 and 8.2 A and two halos at 3.5 and 4.2 A are observed for 1,Cu. The dihydrogeno-derivative leads to a similar pattern but only one halo is noticed at 4.2 A. The mesophases are constituted of two-dimensional square lattices superposed in a staggered conformation.

After a survey of the in-situ techniques used to probe the structure of electrochemical interfaces, we present new results obtained by specular X-ray reflectivity on the liquid-vapor, the liquid-gas and, for the first time, the liquid-water and liquid-electrolyte interface of mercury.

Various techniques for acquiring EXAFS data are examined and their relative advantages and disadvantages delineated; particular attention is focused on in-situ methods. Finally a survey is presented of potentiality and limitation in the determination of the local environment in passive layers by EXAFS spectroscopy.

X-ray diffraction measurements were performed at atmospheric pressure on a high-density form of amorphous ice obtained by pressurizing crystalline ice Ih at 77 K, up to 2 GPa. The low--momentum-transfer region of the determined structure factor is quite different from that corresponding to the low-density form of amorphous ice. However, the nearest-neighbor distance and coordination number are almost unchanged. The high density of this form of amorphous ice is explained by the strong distortion of the 0-0-0 angles from the ideal tetrahedral value.

We built a special Langmuir through allowing the use of X-ray reflectivity. Using the device we studied for the first time the density profile of a Langmuir monolayer directly on water. This experiment opens new prospects in particular to measure the roughness of solid films on water subphase.

The crystal structure of the metastable β-phase of toluene is determined from single crystal X-ray diffraction data using a Monte-Carlo method coupled to a constrained leastsquares refinement. At 105 K β-toluene is orthorhombic (space group Pbcn ; a = 13.85 A, b = 11.42 A, c = 7.39 A ; Z = 8). Relations between the packing of the molecules in this modification and in the normal crystalline α-phase are discussed.

An attempt is made to compare the structures deduced from X-ray measurements on some pure metals, both in the liquid and the non crystalline state. With Ga and Bi, the liquid and the amorphous solid structures show some similarities and seem to be correlated with the solid phase which occurs when crystallisation takes place. Different behaviour is found with Hg : the liquid structure factor differs from the structure factor in the amorphous state whose main peak is symmetric in form.

An apparatus for X-ray reflection measurements is described. The goniometer is designed for studies on liquid and solid surfaces at grazing angles in the range 0-100 mrad. Typical examples using this set up are reported On decrit un dispositif permettant de tester des modeles de profils de densite au voisinage d'une interface solide (ou liquide)-vapeur. Le principe de la methode consiste a mesurer, en fonction de l'angle d'attaque (de l'ordre de quelques mrad), l'intensite reflechie speculairement par une surface plane lorsque celle-ci recoit un faisceau de rayons X. On donne quelques exemples d'application

The crystal and molecular structures of syndiotactic 2,4,6,8-tetraphenylnonane have been determined by direct methods and refinement from X-ray diffraction data. The unit cell is quadratic (space group I 4 1 /g) with, at room temperature, g  13.740, c  27.20 A, V = 5135.7 A, Z = 8 and contains one molecule in the asymmetric unit; the final weighted residual factor is r = 0.065 for 1541 observed reflexions. It is found that the aliphatic chain exhibits a gauche-gauche conformation in the middle of the chain.

Par diffraction des rayons X nous precisons l’identite et les conditions d’obtention des phases haute pression du gallium GaII et GaIII. Jusqu’ici on ne connaissait a haute pression que la structure d’une phase ; nous montrons que cette structure tetragonale centree est celle de GaIII et qu’a 2,6 GPa et 313 K, GaII a une maille cubique centree dont le parametre a est 5,951 + 0,005 A.

An octa-alkylsubstituted derivative of dihydroxo-tin(IV) phthalocyanine is shown to form columnar liquid crystals; polycondensation of the dihydroxo-tin(IV) derivative leads to a spinal columnar mesophase by formation of oxystannyl links between the macrocyclic units.

The x‐ray reflectivity (for Mokα radiation) of liquid mercury as a function of angle of incidence has been measured up to 10 θc (the critical angle θc being equal to 3.76 mrad). Since the x‐ray reflectance is a probe of the properties of the surface, the data can be used to discriminate among models of density profiles in the liquid–vapor interface.

La courbe de fusion du toluene est determinee jusqu’a 9 kbars (900 MN.m-2). Dans cet intervalle de pression et jusqu’a la temperature d’ebullition de l’azote liquide, aucune transition polymorphique n’est detectee.

Dihydroxysilicon(IV) octakis(dodecyloxymethyl)phthalocyanine forms columnar liquid crystal at temperatures ranging from –7 °C to more than 300 °C; polycondensation occurs in the mesophase to yield a series of polysiloxanes which lead to a lamellar liquid crystalline phase.