Understanding the origin of the unique rheological properties of wheat gluten, the protein fraction of wheat grain, is crucial in bread-making processes and has raised questions of scientists for decades. Gluten is a complex mixture of two families of proteins, monomeric gliadins and polymeric glutenins. To better understand the respective role of the different classes of proteins in the supramolecular structure of gluten and its link to the material properties, we investigate here concentrated dispersions of gluten proteins in water with a fixed total protein concentration but variable composition in gliadin and glutenin. Linear viscoelasticity measurements show a gradual increase in the viscosity of the samples as the glutenin mass content increases from 7 to 66%. While the gliadin-rich samples are microphase-separated viscous fluids, homogeneous and transparent pre-gel and gels are obtained with the replacement of gliadin by glutenin. To unravel the flow properties of the gluten samples, we perform shear startup experiments at different shear-rates. In accordance with the linear viscoelastic signature, three classes of behavior are evidenced depending on the protein composition. As samples get depleted in gliadin and enriched in glutenin, distinctive features are measured: (i) viscosity undershoot suggesting droplet elongation for microphase-separated dispersions, (ii) stress overshoot and partial structural relaxation for near-critical pre-gels, and (iii) strain hardening and flow instabilities of gels. We discuss the experimental results by analogy with the behavior of model systems, including viscoelastic emulsions, branched polymer melts, and critical gels, and provide a consistent physical picture of the supramolecular features of the three classes of protein dispersions.

Solitons attract a great deal of interest in many fields, ranging from optics to fluid mechanics, cosmology, particle physics and condensed matter. However, solitons of these very different types rarely coexist and interact with each other. Here we develop a system that hosts optical solitons coexisting with topological solitonic structures localised in the molecular alignment field of a soft birefringent medium. We experimentally demonstrate and theoretically explain optomechanical interactions between such optical and topological solitons, mediated by the local transfer of momentum between light and matter and the nonlocal orientational elasticity of the liquid-crystal phase used in our system. We show that the delicate balance arising from these different contributions to the optomechanical force enables facile dynamical control and spatial localisation of topological solitons. Our findings reveal unusual solitonic tractor beams and emergent light-matter self-patterning phenomena that could aid in creating new breeds of nonlinear photonic materials and devices.

The interfacial region formed in a polymer matrix around nanoparticles (NPs) controls many macroscopic properties of polymer nanocomposites (PNCs). However, understanding the factors controlling the structure and properties of the interfacial region remains a challenge. We demonstrated that the initial trapping of polymer chains at surfaces of NPs in solution strongly affects the macroscopic properties of PNCs. The most surprising result is that the differences in properties of PNCs persist even after an extremely long thermal annealing time. We ascribe the observed changes to the formation of an interfacial layer that is trapped in a deep metastable state already in solution. Furthermore, the presented analysis suggests that the PNC equilibration time is defined by the chain desorption time that can be extremely long and, in some cases, even not accessible on a reasonable experimental time scale. These results highlight the importance of polymer solution concentrations on the formation of an interfacial layer and the macroscopic properties of PNCs.