[en] A review is made of the direct information obtained by small angle neutron scattering about the anisotropy of the components parallel and perpendicular to the orienting magnetic field of the radius of gyration of comb like liquid crystal polymers. The behaviour of the conformation versus temperature is reported for several samples. Until now all samples show an oblate conformation in the smectic phase and probably the whole range of the nematic phase. The results are compared with the available theoretical predictions

[en] Nuclear membranes are prepared by heavy ions irradiation of polymer foils which are subsequently etched by a chemical agent. This allows us to prepare parallel channels with very uniform diameter from a few nm to μm range. Due to their small dispersion these membranes are very suitable for filtration or functionalisation through grafting. Small angle neutron scattering (SANS), performed on the PAXE spectrometer in the Laboratoire Leon Brillouin, Saclay (LLB) and the D11 spectrometer in the Institut Laue Langevin, Grenoble (ILL), allows us to obtain overall information about the channels (albeit in the dual reciprocal space). The large neutron scattering length of hydrogen gives an excellent contrast which makes it possible to get significant spectra from single polymer foils (thickness 12 μm). In the present study we demonstrate that rocking the samples versus the incoming neutron beam allows us to get overall information about the 3D channel structure

[en] The use of four beams separated by a cross-shaped aluminum plate inside the collimator tube, placed at the exit of the 40x40 mm² guide of the Budapest Neutron Center's small-angle neutron scattering (SANS) spectrometer, allowed us to gain a factor close to 4 in neutron intensity. The aluminum separator and the inner surface of the collimator vacuum tube was coated with boron carbide. The cross-section of each beam was 8x8 mm² at the sample position. This setting can be used for measuring large, homogeneous samples, when the measurement does not need high spatial resolution. The beams were focused on the detector by appropriate diaphragms, the collimation length and the sample-detector distance were 4700 mm. In a real SANS experiment we have compared measurements performed on tungsten wire samples with and without beam separator. Using this beam multiplicator the measurement time could be reduced to a quarter

No abstract available

[en] After an introduction about data imaging in general, the principles of imaging data collected via neutron scattering experiments are presented. Some computer programs designed for data imaging purposes are reviewed. (K.A.)

[en] Thermal neutron beams can supply informations about the arrangement of atoms and molecules and about their movement inside the matter. This article treats of the preparation of thermal neutron beams and of the applications that use their penetration and matter activation properties: 1 - thermal neutrons production; 2 - basic properties of thermal neutrons: neutrons scattering, absorbing materials, activating materials, transparent materials, preparation of a neutron beam; 3 - tracks measurement by activation: activation method, measurement of marine pollution by heavy elements, historical evolution of glass composition; 4 - neutron radiography: neutronography, neutronoscopy: viscosity measurement; 5 - cancer treatment. (J.S.)

[en] This article treats of the numerous methods that use the undulatory properties of neutrons (their scattering in matter). Content: 1 - structure of crystallized matter: determination of a magnetic structure, hydrogen localization inside an alloy, 3D mapping of internal stresses inside materials, determination of the crystallographic structure, structure of a monocrystal by 4 circles diffraction; 2 - reflectometry, surface profiles: super-mirrors for neutron guides, giant magnetoresistance thin film devices; 3 - small angle scattering: protein and polyelectrolyte complexes, ropes integrity and microstructure, aggregates growth inside irradiated steels, microstructural evolution of defects inside race car engine pistons; 4 - dynamics: collective mode dynamics - three axis spectrometer, Mn Te magnons in thin film, scattering dynamics - quasi-elastic time-of-flight spectrometer, water diffusion inside cement. (J.S.)

[en] A comblike liquid crystal polymer (LPC) is a polymer on which mesogenic molecules have been grafted. It exhibits a succession of liquid crystal phases. Usually the equilibrium conformation of an ordinary polymeric chain corresponds to a maximum entropy, i.e., to an isotropic spherical coil. How does the backbone of a LCP behave in the nematic and smectic field? Small-angle neutron scattering may answer this question. Such measurements are presented here on four different polymers as a function of temperature. An anisotropy of the backbone conformation is found in all these studied compounds, much more pronounced in the smectic phase than in the nematic phase: the backbone spreads more or less perpendicularly to its hanging cores. A comparison with existing theories and a discussion of these results is outlined

[en] Liquid crystal phases are characterized by a long range orientational order. Numerous studies on liquid crystals under hydrostatic pressure display interesting pressure induced phenomena which seem to indicate that this long range order is disturbed. It is shown for example that re-entrant phases appear and that phase transition temperature shifts are commonly observed. These pressure induced effects result from the packing properties exacerbated by the pressure induction of the molar volume. Despite numerous developments, the structural modifications which accompany these pressure induced effects, as the phase transition temperature shifts, have hardly been investigated. We provide, using neutron diffraction, the physical reasons for these temperature shifts. We report here on the very few structural studies of the influence of hydrostatic pressure on the stability of a liquid crystal phase. This study is carried out using two specifically designed neutron pressure cells reaching pressure values up to 120 MPa. The liquid crystal system is described in terms of pressure-induced correlation lengths and layer spacing, which are the relevant parameters to account for the phase structure. It will be shown that the structural investigation is particularly noteworthy in the lamella phase since the characteristic lengths can be tremendously modified under pressure, underlining a correlated change of dynamics. In the case of high molecular weight liquid crystals (side-liquid crystal polymers), it will be shown that the re-entrant nematic-smectic transition is unchanged with respect to the pressure, indicating that the pressure induced reduction of the specific volume concerns the polymer component only

[en] A mapping of the intensity of neutrons scattered by the phonon branches nusub(5)sup(a), nusub(9)sup(a) along the csup(*) axis, in uniaxial deuterated polyethylene, has been measured in the anticrossing region, at nitrogen and room temperatures. The predicted gap between the phonon dispersion curves has been proven at both temperatures. It is smaller than has been foreseen. Only the nusub(9)sup(a) branch is well described by a theoretical model. The nusub(5)sup(a) branch seems to be rather sensitive to temperature. (author)