Natural protein sources often display a huge complexity, being composed of a blend of polypeptides of various molecular weight, pHi and charge density. Gluten, the proteins extracted from wheat flour is one of such. Gluten is widely used for its viscoelastic properties as an improver of cereal products (bread, pastry, etc.). It is composed of two classes of proteins, named gliadin and glutenin, similar in their amounts in glutamine (30%) and proline (10%). The more than 25 different polypeptides belonging to the gliadin class are hard to fractionate into individual components because of high redundancy in the primary sequences. Glutenin are in the form of polymers made from several distinct polypeptides concatenated through inter-chain disulfide bonds. Their molecular weights are evenly distributed from 100 kg/mol to 7,000 kg/mol.While it is well established that gliadin confers viscosity to gluten whereas glutenin polymers are at the origin of its elastic resistance, the interactions existing between both classes of gluten protein remain unknown. We previously showed by SLS and multi-angle DLS that gluten proteins suspended in ethanol/water (50/50, v/v), a theta solvent, includes large proteins assemblies (26,000 kg/mol, Rh 100nm) displaying an internal dynamic1. To get a better insight of the composition of those assemblies, we combined biochemical and physicochemical approaches. On the one hand, gluten proteins suspended in ethanol/water were fractionated by Asymmetrical- Flow-Field-Flow Fractionation (A4F) coupled to UV, SLS and QELS detectors. On the other hand, gluten proteins were partitioned by liquid-phase decomposition in respect with temperature. Protein composition of partitioned phases and eluting fractions recovered from A4F were characterized by size-exclusion chromatography. A specific interaction between omega-gliadin and glutenin polymers was evidenced.This result strengthens a very recent study that demonstrates a significant positive correlation between glutenin polymeric proteins, the ω‐gliadin fraction, and dough properties.

A combined small-angle scattering of neutrons (SANS) and X-rays (SAXS) study of thestructure of polymer layers pre-adsorbed on silica nanoparticles (NP) which are subsequentlyincorporated into polymer nanocomposites (PNCs) is presented. Pre-adsorbed chains are foundto promote ideal dispersion, before desorption in the late stages of nanocomposite formation.The microstructure of the interfacial polymer layer is characterized by detailed modeling of X-rayand neutron scattering. Only in ideally well-dispersed systems a static interfacial layer ofreduced polymer density over a thickness of ca. 2 nm is evidenced based on the analysis with aform-free density profile optimized using reverse Monte Carlo simulations. This interfacialgradient layer is found to be independent of the thickness and mass of the initially adsorbedpolymer, but appears to be generated by out-of-equilibrium packing and folding of the preadsorbedlayer. The impact of annealing is investigated to study the approach of equilibrium,showing that initially ideally well-dispersed systems adopt a repulsive hard-sphere structure,while the static interfacial layer disappears.In parallel, SANS and the use of zero average contrast conditions allow the measurement ofchain conformation in the PNCs with and without pre-adsorption. Surprisingly, we evidenced thespontaneous formation of thermally-stable adsorbed layers in PNCs containing matrix chains ofdifferent mass, whereas a symmetric matrix of identical chain masses does not show this effect.This study contributes thus to the fundamental understanding of the interplay betweeneffects which are decisive for macroscopic material properties: polymer-mediated interparticleinteractions, and particle interfacial effects on surrounding polymer.

Despite the relevance to environmental, biological and industrial processes, the motion of a colloidal particle close to a fluid interface and the way it interacts with the water surface are still largely elusive and intriguing physical phenomena.We explored the system of individual colloidal particles close to an air-water interface by recording highly resolved 3D trajectories through a dual wave reflection interference setup (DW-RIM). Contrary to other established experimental techniques, DW-RIM allows accurate measurements of the absolute particle-interface distance and thus does not require any calibration or assumption to know the location of the interface. The particle-interface system shows two different potential energy landscapes resulting to two different equilibrium particle-interface distances. The larger one can be fairly explained by Van der Waals and electrostatic interactions combined with gravity. The shorter one highlights the existence of an unexpected additional attractive interaction. Surface heterogeneities as possible origin of such an interaction are considered and discussed.Concerning the friction the particle undergoes, the air-water interface peculiarly acts as a slip boundary for the particle motion parallel to the interface and as a no-slip boundary for the perpendicular motion. This experimental result is rationalized considering recent models based on surface incompressibility.

To date, aqueous stable graphene flakes solutionscan be obtained by simple REDOX reactions.1–5 Most of the current applications regardinggraphene require ordered nanostructuredcomposites materials. Liquid crystal phases orderingrepresent an opportunity to arrange theminto macroscopic assemblies with long-rangeordering. 1,2 Preparing organized materials andthin films from these dispersions then requires agood control of the liquid crystal ordering duringthe deposition and the drying of the films. As amatter of fact, it turns out that graphene flakeseasily align at high shear.3,4 On the other hand,Graphene Flakes Liquid Crystals (GFLC) exhibita very interesting behaviour at low shear or undersmall displacements, thin films often showspeculiar patterns (such as the periodic texturesshown in Fig.72-72). We have shown how tocreate and stabilize large-sized periodic texturesin GFLC. The patterns have been characterizedunder optical and electronic microscopies. Theirstability can be explained by the competition betweenthe anchoring field of the substrate andthe presence of a yield stress resulting fromthe peculiar elastic and rheological properties ofthe GFLC. Our findings also clarify why longstandinghypotheses on the presence of exoticphases1 at large concentrations are present inthe literature.
References[1] Zakri, C.; Blanc, C.; Grelet, E.; Zamora-Ledezma, C.; Puech, N.; Anglaret, E.; Poulin, P. Philosophical Transactions of theRoyal Society A: Mathematical, Physical and Engineering Sciences 2013, 371, 20120499..
[2] Zamora-Ledezma, C.; Puech, N.; Zakri, C.; Grelet, E.; Moulton, S. E.; Wallace, G. G.; Gambhir, S.; Blanc, C.; Anglaret, E.;Poulin, P. The journal of physical chemistry letters 2012, 3, 2425–2430..
[3] Poulin, P.; Jalili, R.; Neri, W.; Nallet, F.; Divoux, T.; Colin, A.; Aboutalebi, S. H.; Wallace, G.; Zakri, C. Proceedings of theNational Academy of Sciences 2016, 113, 11088–11093..
[4] Zamora-Ledezma, C.; Jeridi, H.; Anglaret, E.; Blanc, C. Orientations and periodic textures in graphene liquid crystals. 27thInternational Liquid Crystal Conference (ILCC2018). 2018..
[5] Xu, Z.; Gao, C. Nature communications 2011, 2, 571.

Heliconal nematic twist bend (NTB) phases are usually not well oriented in planar commercial cells, even in thin (~1 µm) ones where a micron-sized periodic texture is usually observed [1,2,3] (see Fig.1-a). The origin of the stripe patterns is attributed to the rapid shrinking of the pseudo-layers below the N-NTB phase transition temperature, which yields an undulation instability. The observed periodicity is found to be twice the cell gap [1].
We have explored the effect of the strength of the anchorings of the substrates on the resulting patterns. We used polymer aligning layers of tunable azimuthal and zenithal strengths to design liquid crystal cells with surface anchorings ranging from ultraweak to strong. We then have studied the patterns formed by the NTB phase of 1,7-bis-4-(4-cyanobiphenyl) heptane (CB7CB). We will show how the period of the stripes can be varied in a large range in cells of the same thickness but with different anchoring preparations. With adequate anchoring conditions (see Fig.1-b-c), an excellent and spontaneous planar alignment of the NTB phase of CB7CB can be obtained much below the phase transition temperature.
[1] Panov V.P. et al; Spontaneous Periodic Deformations in Nonchiral Planar-Aligned Bimesogenswith a Nematic-Nematic Transition and a Negative Elastic Constant; Phys. Rev. Lett. ; 105; 167801; 2010.
[2] Challa P. K. et al; Twist-bend nematic liquid crystals in high magnetic fields; Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys.; 89; 060501; 2014.
[3] Vaupotič N. et al.; Polarization Gratings Spontaneously Formed from a Helical Twist‐Bend Nematic Phase; Chem. Phys. Chem.; 19; 2566; 2018.

Heliconal nematic twist bend (NTB) phases are frequently found at high temperatures. In the last years the search of stable room-temperatures NTB phases has led to the synthesis of new compounds [1] and to the design of multicomponent systems. Mixtures of NTB compounds with nematogens ,such as 4-Cyano-4'-pentylbiphenyl (5CB) dimeric liquid crystal 1,7-bis(4-cyanobiphenyl-4-yl) heptane (CB7CB) decrease strongly the temperature range of the NTB phase and tune the optical, thermal and dielectric properties of NTB [2]. In this work we have explored the physical properties of mixtures of CB7CB with several smectogens with a particular focus on 4′-octyl-4-biphenylcarbonitrile (8CB). The 8CB/CB7CB phase diagram reveals striking features compared to the 5CB/CB7CB one. Despite their macroscopic resemblance, SmA and NTB domains appear incompatible and remain separated by a nematic phase that extends to very low temperature (-20°C) at a CB7CB fraction of ϕ_c≈20%. We have characterized the optical, thermal, dielectric and anchoring properties of the N and NTB phases of the mixtures. Compared to the pure CB7CB system, the N phase shows unusual behavior over a large range of composition and reveals strong pre-transitional effects when approaching ϕ_c. We also found that, for specific aligning substrates, adding 8CB to CB7CB drastically changes the anchoring properties (fig1) facilitating homeotropic alignment.
[1] Yuan Wang, Quan Li; Room temperature heliconical twist-bend nematic liquid crystal; Cryst. Eng. Comm; 17; 2778-2782; 2015.
[2] Nina Trbojevic and Mamatha Nagaraj; Dielectric properties of liquid crystalline dimer mixtures exhibiting the nematic and twist-bend nematic phases; Phys. Rev. E ;96; 052703; 2017.

The conformation of single-chain nanoparticles (SCNPs) in presence of linear polystyrene crowding molecules has been studied by small-angle neutron scattering under contrast-matching of the crowders. A model describing the scattering of aggregating polydisperse SCNPs has been developed, resulting in the determination of the potentially squeezed size of the individual SCNPs within aggregates, their local chain statistics, and the average aggregation number, as a function of crowding. Two different crowders – of low and high molecular weight, respectively – are shown to have a different effect: while long chains tend to impede their aggregation above their overlap concentration, short ones are found to mediate depletion interactions leading to aggregation. Self-imposed crowding within the aggregates has a similar impact on chain conformation independently of the crowding of the surrounding medium. Our results are compared to recent simulations and shall contribute to the microscopic understanding of the phase behavior of soft intrinsically disordered nano-objects, and in particular the effect of crowding on biomacromolecules.