[en] Small-angle Neutron scattering is the unique method which allows the determination of polymer conformation in the bulk state. This method has been applied to several kinds of liquid crystalline polymers. Results concerning side-chain liquid-crystal polymer, main-chain liquid-crystal polymer and combined liquid-crystal polymers, are reported. It is shown that the polymer conformation is largely dependent on the insertion site of the liquid crystal molecule and of the structure of the meso-phase. (author). 11 refs

[en] We determined the evolution of the main-chain conformation and of the liquid crystalline structure of a liquid crystal poly-methacrylate in the smectic phase, versus shear rate. It is shown that the macroscopic shear was transmitted to the smectic layers which ensured an efficient shear of the polymer main-chains. The outcome was a macroscopic orientation of the smectic mono-domains with the smectic planes parallel to the shear plane. The polymer main-chains already confined by the mesogenic layers, were in addition, the more elongated along the velocity direction that the stronger, the shear was. These results were obtained in situ by the observations in the shear plane and in the vorticity plane. (authors)

[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] 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] Quenched isotropic melts of side-chain liquid-crystal polymers reveal surprisingly an anisotropic polymer conformation. This small-angle neutron-scattering (SANS) result is consistent with the identification of a macroscopic, solidlike response in the isotropic phase. Both experiments (rheology and SANS) indicate that the polymer system appears frozen on millimeter length scales and at the time scales of the observation. This result implies that the flow behavior is not the terminal behavior and that cross-links or entanglements are not a necessary condition to provide elasticity in melts

[en] A specific lithic manufacturing of flints has emerged in the South of France from 4200 to 3500 ca B.C. This treatment involving a smooth thermal exposure procures an improvement of the ease of detachment and of the cutting properties of the flints. The origin of these new properties remains misunderstood. High resolution large angle neutron scattering (Barotron detector) is used to describe the structural modifications occurring after the thermal treatment. The comparison of the scattering exhibited by native silica flints and flints treated at the Neothilic age does not show a structural change but indicates a significant increase of the quantity of liquid water trapped in the treated flint. It is suggested that the Neolithic treatment was proceeded in several steps including a prior wetting of the flint and then a thermal treatment closing the porosity and trapping the liquid water inside the silica flint. (paper)

[en] We present here results of small-angle neutron scattering (SANS) investigation of partially and fully yttria stabilized zirconia (PYSZ and FYSZ, respectively) turbine blade coatings (TBC). The samples have been prepared by electron beam physical vapour deposition method (EB-PVD) with various setup parameters. Structure parameters of porosity have been studied in-situ with high-temperature furnace. Temperature dependence of specific surface and anisotropy parameter of porosity has been obtained. Differences in character of microstructural morphology changing with in-situ thermal treatment as well as open and closed porosity ratio in PYSZ and FYSZ has been described and discussed.

[en] Small Angle Neutron Scattering experiments were carried out on liquid crystalline ''side-on fixed'' polyacrylates: we observe that the polymer backbone adopts a prolate conformation in the nematic phase. Such anisotropy of the global backbone is larger for smaller spacer lenght. In every case we measure at low temperatures a large chain extension as previously described in polysiloxanes. (orig.)

[en] The structure of an achiral smectic-C liquid crystal confined in nanocylinders with a planar surface anchoring is studied by small angle neutron scattering. We observe an invariant alignment of the nematic director with the pore axis, that promotes an original chevron structure with revolution symmetry