M. Bée

University Joseph Fourier - Grenoble 1, Grenoble, Rhône-Alpes, France

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Publications (106)175.96 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The nitroxide C9H16NO2 (tano) forms channel inclusion compounds with a large range of linear chains or slightly branched molecules. All of them present disorder phenomena of the guest chains in the channels of the structure, but also of the host matrix molecules from one chiral form to the other. The evolution of this disorder as a function of the temperature is accompanied by one or two phase transitions above 100 K. The incoherent quasielastic neutron scattering (IQNS) technique was used to study the motion of the tano molecules for the tano/1-bromohexadecane and the tano/1-bromodecane systems in their low, intermediate and high temperature phases. The experiments were carried out on a polycrystalline sample at the Institut Laue–Langevin in Grenoble using the time-focusing time-of-flight spectrometer IN6 with a temperature ranging from 103 K to 300 K. The motion of the guest chains also was shown. The results are examined in terms of the general model proposed in an earlier IQNS study of other tano/alkane compounds with shorter included chains and the original features associated with the chain length are discussed.
    Molecular Physics 12/2010; July 1(1997):681-688. · 1.67 Impact Factor
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    ABSTRACT: QENS: Future prospects on High-reolsution Inelastic Neutron Scattering, Eds J Colmenero, A Alegria, F J Bermejo (World Scientific) 107 (1994)
    ChemInform 01/2010; 27(4).
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    ABSTRACT: The structure of a family of copolyimides in which are alternating stiff/redox pyromellitimide units and flexible/solvating polyethyleneoxide (PEO) strands were studied by using wide angle and small angle X-ray scattering techniques and is fully discussed. It is shown that the rich variety of structures exhibited by these compounds can be understood by considering the dramatic change of flexibility of the chain induced by the variation of the length of the PEO strand compared to that of the pyromellimide segment. In this respect, concerning the compounds which exhibit fully amorphous structures a better understanding of their structural behavior can be obtained in the framework of Flory's theory of semi-rigid polymers. In this approach, the degree of flexibility of the chain is mainly resulting from the relative amount of flexible units constituting the repetition unit of the polymer chain. The final structural mode adopted by each compound in the solid state is then directly a consequence of this intrinsic property of the chain. The introduction of a lithium salt in contact with the copolymer chains induces some structure changes which can also be explained by the modification of the degree of flexibility of the chain. It is found that the best performances in terms of electroactivity and mixed conduction are precisely obtained with the only compound which keeps full amorphicity in absence and in presence of the lithium salt.
    Electrochimica Acta - ELECTROCHIM ACTA. 01/2007; 53(4):1497-1502.
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    ABSTRACT: Numerical methods of molecular dynamics have been combined to measurements of X-ray and neutron scattering in order to obtain a realistic view of structural and dynamical disorder properties of conducting compounds of so called “plastdoped” poly(aniline)s. This combination allowed us to propose for the whole family of these compounds one generic model of a layered structure in which exist statistical fluctuations of the electronic density along the stacking direction of alternating molecular layers. The most part of the dynamics in the 10−13–10−9 s time range concerns the motions of protons borne by the flexible tails of doping counter-ions contained in the structure. We found that the molecular dynamics is characterized by both broad time and spatial distributions. These experimental facts coupled to those obtained with electrical conductivity measurements indicate that the high mobility of the counter-ion sublattice seems to be a prerequisite to promote a global metal like electronic behaviour of the polymer films.
    Macromolecular Symposia 01/2006; 241(1):28-33.
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    ABSTRACT: Calorimetric (DTA), infrared, Raman and inelastic neutron scattering (INS) measurements have been performed for the trimethyloxosulphonium iodide compounds (CH3)3SOI and (CD3)SOI over the range 10–450 K. Two solid-solid phase transitions were found at about 200 and 250 K and the vibrational study showed that only the low-temperature crystalline form (III) is completely ordered. From a temperature dependence study of the optical and INS spectra it is concluded that methyl group reorintations are mainly involved in the phase (III)⟷phase (II) transition, while the whole molecule reorientations about the three-fold axis, partly involved in the phase (II)⟷phase (I) transformation, must be much slower than and decoupled from methyl motions. Finally, the potential barrier height against methyl rotations has been estimated to 13.3 kJ mol−1 from the observed torsional frequencies and compares favourably with the activation energies derived from previous NMR experiments (10.9 kJ mol−1) and from quasi-elastic neutron scattering results (10.6 kJ mol−1).
    Journal of Raman Spectroscopy 04/2005; 16(1):44 - 56. · 2.68 Impact Factor
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    ABSTRACT: Proton dynamics in films of poly(aniline) "plastdoped" with di-esters of sulfophthalic (or sulfosuccinic) acids have been investigated by using quasi-elastic neutron scattering techniques. A broad time range (10(-13)-10(-9) s) has been explored by using four different spectrometers. In this time range, the dynamics is exclusively due to protons attached to the flexible tails of the counter-ions. A model of limited diffusion in spheres whose radii are distributed in size gives a realistic view of the geometry of molecular motions. However, it is found that the characteristic times of these motions are widely distributed over several orders of magnitude. The time decay of the intermediate scattering function is well described by a time power law. This behaviour is qualitatively discussed in connection with the structure of the systems and by comparison with other so-called complex systems.
    Physical Chemistry Chemical Physics 03/2005; 7(6):1235-40. · 4.20 Impact Factor
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    ABSTRACT: We present new McStas simulations of the back-scattering thermal neutron spectrometer IN13 to evaluate the advantages of a new temperature gradient monochromator relative to a conventional one. The simulations show that a flux gain up to a factor 7 can be obtained with just a 10% loss in energy resolution and a 20% increase in beam spot size at the sample. The results also indicate that a moderate applied temperature gradient is sufficient to obtain this significant flux gain.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2005; 544(3):649-658. · 1.14 Impact Factor
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    ABSTRACT: Dynamics of counter-ions in poly(aniline) doped with di-(2-butoxyethoxyethyl)ester of 4-sulfophthalic acid have been simulated using force field based molecular dynamics involving a semi-empirical charge equilibration procedure and charge rescaling based on DFT calculations. Due to particular relaxational and structural characteristics of such “plastdoped” poly(anilines), these simulations have proved to be a very effective tool for reproducing the main structural and dynamic features of the material. The experiment/simulation comparison for dynamics is very good in the 10−10–10−13s time range. In particular, mean square displacements extracted from the molecular dynamics simulations for atoms in the counter-ions are in good agreement with the analytical model used to analyse the quasi-elastic neutron scattering data. The use of a larger simulation box and longer simulation time give good agreement in the extended time domain and reveal a dynamical heterogeneity between the counter-ions that was not foreseen in the analytical model.
    Chemical Physics 01/2005; · 1.96 Impact Factor
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    ABSTRACT: Using the quasielastic neutron scattering technique on the 10−12 s time scale, the dynamics of highly conducting free-standing films of doped polyaniline have been studied in detail. The latter are protonated with sulphonated organic acids made of flexible molecules which also play the role of plasticizer of the system. While polymer chains appeared immobile, the study of the dynamics of these counter-ions reveals a glass transition temperature which corresponds to the change in the electronic conductivity of the film. Competing interactions in between the counter-ions and between polymer chains and counter-ions limit the available space for alkyl chains to move around. A description of the dynamics is proposed on the basis of a model where protons undergo a local diffusion inside individual spheres whose radii depend explicitly on their position on the molecule. When the temperature is decreased, only protons attached to the aliphatic tails explore a significant space while the others are progressively frozen. Refinement of the neutron data permit one to access the radii of the sphere and the diffusion constant as functions of temperature.
    Philosophical Magazine A 05/2004; 84(13-16):1547-1554.
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    ABSTRACT: The use of IN13 backscattering spectrometer at ILL is getting larger and larger, in particular in the biological community. Indeed, it explores a time–space window of a few angstroms for times up to 100 ps, which is well adapted to the motions in biological samples. On the other hand, its major drawback is a quite low neutron flux on the sample, implying long acquisition times which impose limits on experimental data obtainable and important sample mass. A major upgrade of the instrument is now processing, aiming to higher neutron flux and improvement of instrument versatility, thus making of IN13 a very competitive instrument.
    Physica B Condensed Matter 01/2004; 350(1). · 1.28 Impact Factor
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    M. Bee
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    ABSTRACT: Incoherent quasi-elastic neutron scattering (QENS) has undergone a remarkable development since the 1970s and 1980s when the resolution of spectrometers first allowed an accurate analysis of the exact shape of the energy spectra. These pioneering years were characterized by a multitude of theoretical works and the invention of a considerable number of dynamical models adapted to more and more complex physical situations. The scattering laws concerned long-range diffusion of atoms or molecules in various environments as well as localized rotational motions of chemical groups or of whole entities. Today, QENS is still as active and thriving, but it deals with increasingly complex systems. It has moved towards more applied subjects directly related to industry, such as the development of high-performance materials and, recently, to biological macromolecules. These new fields of investigation are the natural consequence of the continuous building of new spectrometers with improved performances. The interpretation of results is often confronted with problems related to the complexity of the samples under study, and new approaches to data analysis have been undertaken. Several examples of studies in QENS were chosen to illustrate the continued importance of this technique in the investigation of diffusive processes. Original and recently developed theoretical and numerical approaches are described. In conclusion, general trends on the future of this technique are outlined.
    Chemical Physics 01/2003; 292(2):121-141. · 1.96 Impact Factor
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    Synthetic Metals - SYNTHET METAL. 01/2003; 135:259-260.
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    ABSTRACT: Using a neutron backscattering spectrometer, the temperature dependence of mean-square atomic displacements derived from window-integrated quasielastic spectra was measured for two D2O-hydrated proteins: crambin and glutathione S-transferase. Analyses show that the anharmonic dynamics observed around and above 200 K is consistent with a description in terms of proton/deuteron jumps within asymmetric double-minimum potentials. Also determined were activation energies along with estimates of effective masses and average oscillator energies.
    Chemical Physics 01/2003; · 1.96 Impact Factor
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    Synthetic Metals - SYNTHET METAL. 01/2003; 135:323-324.
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    ABSTRACT: Polyaniline (PANI) has been protonated (doped) with phthalosulfonic acid and sulfosuccinic acid diesters. Freestanding films exhibiting high electrical conductivity and good plasticity were obtained. The dynamics of protons attached to the alkyl chains of these “plastdopants” has been studied by using quasielastic neutron scattering techniques. A glass transition was thus detected at a temperature corresponding to that measured by DSC. This dynamical transition occurred in the temperature range, in which both a thermochromism and an insulator–metal electrical transitions (IMT) were also observed. The local diffusive motions of these protons are described in terms of diffusion within spheres whose temperature dependent radii are distributed in size along the alkyl chains.
    Chemical Physics 01/2003; 292(2):355-361. · 1.96 Impact Factor
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    ABSTRACT: Conducting polyaniline protonated with sulphonic flexible counter-ions was investigated by quasielastic incoherent neutron scattering. In addition to their role in electrical properties, the flexible counter-ions also increase the elasticity of the samples. As in the case of more rigid counter-ions, polymer chains appear as very stiff objects whose dynamics is completely outside the investigated time scale. Conversely, the counter-ion dynamics was proved to be of major importance in charge transport since a dynamical transition is observed precisely in the temperature range where the electronic properties change from a metallic to a semiconducting regime.
    Applied Physics A 11/2002; 74:s402-s404. · 1.69 Impact Factor
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    ABSTRACT: The rotational and translational dynamics of methanol adsorbed on H-ZSM-5 have been studied by incoherent quasi-elastic neutron scattering. From the variation of the elastic incoherent structure factor (EISF), two methanol species are characterized: (i) adsorbed molecules interacting with the zeolite via hydrogen bonds and (ii) mobile molecules diffusing within a sphere of diameter 4.8 +/- 0.4 A. The proportion of mobile molecules was determined, in the temperature range 273-425 K, from the variation of the experimental EISF with temperature. The correlation times have been obtained for the two methanol species, for the rotational motions, by fitting the quasi-elastic profile. The translational motion has been characterized by studying the same system on a spectrometer with a longer time scale. The methanol molecules jump from one site to another, across the channel (jump distance approx. = 5 A), and they diffuse along the channels with a diffusion coefficient of the order of 10⁻⁷ cm² s⁻¹. 35 references, 13 figures.
    The Journal of Physical Chemistry. 04/2002; 90(6).
  • The Journal of Physical Chemistry. 04/2002; 98(17).
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    ABSTRACT: The availability of a high momentum transfer (0.3-1)&#55eV, makes the spectrometer IN13 particularly suited to the study of the local dynamics of soft matter, such as polymers and biological systems. In the present configuration the performance of the instrument is overall limited by the low incident flux. A progressive upgrade of the instrument is planned in order to improve this and also to increase the instrument versatility. In this way, different possibilities other than the standard configuration, will be available in order to allow for the best compromise to be defined between flux, energy resolution and Q-range for each experiment. The first step of this project consists of simulating the instrument and the different modifications envisaged. The results of our Monte Carlo simulations of the primary spectrometer together with data from experimental tests show that IN13 could be modified in order to obtain a gain in neutron flux up to a factor of five.
    Applied Physics A 01/2002; 74. · 1.69 Impact Factor
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    ABSTRACT: Molecular motions in mono-hydrated racemic camphor sulphonic acid (±)-10-C10H16O4S−–H3O+ which is abbreviated as (CSA–H2O) were investigated using incoherent neutron scattering techniques. Analysis of the intensity of the purely elastic scattering over a wide temperature range (4–340 K) carried out with a high-resolution backscattering spectrometer revealed the onset of molecular motions at ca. 100 K which could be observed on the 10−10 s time-scale up to T=180 K. These motions were identified as 120° jumps of the methyl groups. Quasielastic measurements using both the backscattering and the time-of-flight techniques enabled to study this movement from 150 to 340 K. The corresponding characteristic time was found to follow an Arrhenius law with an activation energy . All the methyl groups appear as dynamically equivalent. That result is at contrast with earlier studies on conducting polymers where CSA was introduced as a counter-ion and for which the intermolecular effects were found to strongly influence the dynamics. Inspection of the low frequency part of the vibrational spectrum evidences deformations of the C–C–S angle and rotational oscillations of the hydration molecules.
    Chemical Physics 01/2002; 277(2):211-224. · 1.96 Impact Factor

Publication Stats

399 Citations
175.96 Total Impact Points

Institutions

  • 1989–2005
    • University Joseph Fourier - Grenoble 1
      Grenoble, Rhône-Alpes, France
  • 1982–2005
    • Institut Laue-Langevin
      Grenoble, Rhône-Alpes, France
  • 1980–2000
    • Université des Sciences et Technologies de Lille 1
      • Unité de Dynamique et de Structure de Matériaux Moléculaires (UDSMM)
      Lille, Nord-Pas-de-Calais, France
  • 1998
    • University of Leipzig
      • Faculty of Physics and Earth Sciences
      Leipzig, Saxony, Germany
  • 1992
    • French National Centre for Scientific Research
      • Institut de recherches sur la catalyse et l`environment de Lyon (IRCELYON)
      Lutetia Parisorum, Île-de-France, France