The origin of the unique rheological properties of wheat gluten, the water-insoluble protein fraction of wheat grain, is crucial in bread-making processes and questions scientists since the 18th century. Gluten is a mixture of two types of proteins, monomeric gliadins and polymeric glutenins, formed by subunits linked via disulfide bonds. To better understand the respective role of gliadins (Gli) and glutenins (Glu) in the supramolecular structure of gluten and its link to rheology, we have developed a model gluten system using a food-grade solvent, which allows quantitative comparisons with theoretical models for synthetic polymers [1]. Thanks to an experimental protocol based on a liquid-liquid phase separation, we can extract, from industrial gluten, gluten protein fractions with contrasted mass ratios Glu/Gli (from 0.04 to 2). Stable gluten protein suspensions in a water/ethanol mixture solvent over a wide range of concentrations can be produced. Using scattering techniques, we demonstrate that blends of Gli and Glu exhibit features characteristic of branched flexible polymer chains in a good solvent, and form in a dilute regime large Glu-rich protein assemblies [2]. In the semi-dilute regime, we evidence the existence of large zones (of typical size 60 nm) rich in hydrogen bonds [3]. We show that hydrogen bonds are responsible for the spontaneous sample gelation, whose concentration dependence can be quantitatively accounted using percolation theories developed for polymer gels [4]. Overall, our experimental results illustrate the relevance of model gluten gels to unravel the unique and complex behavior of gluten. [1] Banc, Dahesh, Wolf, Morel, Ramos. Journal of Cereal Science 75, 175 (2017). [2] Dahesh, Banc, Duri, Morel, Ramos. J Phys Chem B 118, 11065 (2014). [3] Banc, Charbonneau, Dahesh, Appavou, Fu, Morel, Ramos. Soft Matter 12, 5340 (2016). [4] Dahesh, Banc, Duri, Morel, Ramos. Food Hydrocolloids, 52, 1 (2016).

Materials are the key roadblocks for the commercialization of energy conversion devices in fuel cells andsolar cells. Significant research has focused on tuning the intrinsic properties of materials at the nanometerscale. The soft template mediated controlled fabrication of advanced nanostructured materials isattracting considerable interest due to the promising applications of these materials in catalysis and electrocatalysis.Swollen hexagonal lyotropic liquid crystals (SLCs) consist of oil-swollen surfactant-stabilized1D, 2D or 3D nanometric assemblies regularly arranged in an aqueous solvent. Interestingly, the characteristicsize of the SLCs can be controlled by adjusting the volume ratio of oil to water. The non-polarand/or polar compartments of the SLCs can be doped with guest molecules and used as nanoreactorsfor the synthesis of various metals (Pt, Pd, Au, etc.), conducting polymers and composite nanostructureswith controlled size and shape. 1D, 2D and 3D mono- and bimetallic nanostructures of controlled compositionand porosity can also be fabricated. These materials have demonstrated impressive enhancementsof their electrochemical properties as compared to their bulk counterparts and have been identifiedas promising for further implementation in energy harvesting applications. In this review article,recent research materials are described regarding the development of functional materials with muchimproved performances for catalysis applications. This review addresses a brief overview of swollen hexagonalmesophases as nanoreactors, describes examples of nanostructured materials synthesized inthese nanoreactors, shows several examples of the energy conversion applications in solar light harvesting,fuel cells etc. and also summarizes the associated reaction mechanisms developed in the recent literaturefor enhanced catalytic activity.

A novel experimental technique based on in situ AFM monitoring of the mechanisms of damage and the strain fields associated to the slow steady-state propagation of a fracture in glassy polymers is presented. This micron-scale investigation is complemented by optical measurements of the sample deformation up to the millimetric macroscopic scale of the sample in order to assess the proper crack driving conditions. These multi-scale observations provide important insights towards the modeling of the fracture toughness of glassy polymers and its relationship with the macromolecular structure and non-linear rheological properties. This novel technique is first tested on a standard PMMA thermoplastic in order to both evaluate its performance and the richness of this new kind of observations. Although the fracture propagation in PMMA is well known to proceed through crazing in the bulk of the samples, our observations provide a clear description and quantitative evaluation of a change of fracture mechanism towards shear yielding fracture accompanied by local necking close to the free surface of the sample, which can be explained by the local change of stress triaxiality. Moreover , this primary surface necking mechanism is shown to be accompanied by a network of secondary grooves that can be related to surface crazes propagating towards the interior of the sample. This overall scenario is validated by post-mortem fractographic investigations by scanning electron microscopy.

An original setup combining a very stable loading stage, an atomic force microscope and an environmental chamber, allows to obtain very stable sub-critical fracture propagation in oxide glasses under controlled environment, and subsequently to finely characterize the nanometric roughness properties of the crack surfaces. The analysis of the surface roughness is conducted both in terms of the classical root mean square roughness to compare with the literature, and in terms of more physically adequate indicators related to the self-affine nature of the fracture surfaces. Due to the comparable nanometric scale of the surface roughness, the AFM tip size and the instrumental noise, a special care is devoted to the statistical evaluation of the metrologic properties. The 2 roughness amplitude of several oxide glasses was shown to decrease as a function of the stress intensity factor, to be quite insensitive to the relative humidity and to increase with the degree of heterogeneity of the glass. The results are discussed in terms of several modeling arguments concerning the coupling between crack propagation, material's heterogeneity, crack tip plastic deformation and water diffusion at the crack tip. A synthetic new model is presented combining the predictions of a model by Wiederhorn et al. [1] on the effect of the material's heterogeneity on the crack tip stresses with the self-affine nature of the fracture surfaces.