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Production scientifique
Matière Molle & Verres
(46) Production(s) de l'année 2022
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Pseudospin-phonon dynamics in lead halide hybrid perovskites
Auteur(s): Even Jacky, Hehlen B., Bourges Philippe, Ruffle B., Katan Claudine, Létoublon Antoine
Conférence invité: Nanoge HPATOM2 (online, FR, 2022-02-02)
Ref HAL: hal-03562709_v1
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Résumé: The low frequency lattice vibrations and relaxations are investigated in single crystals of the four 3Dhybrid organolead perovskites, MAPbBr3, FAPbBr3, MAPbI3, and FAPbI3, at the Brillouin zone centerusing Raman and Brillouin scattering and at the zone boundary using inelastic neutron scattering. Thetemperature dependence of the PbX6 lattice modes in the four compounds can be renormalized intouniversal curves and no soft vibration is observed excluding a displacive-like transitional dynamics. Thereorientational (pseudospin) motions of the molecular cations exhibit a seemingly order-disordercharacter recalling that of plastic crystals, but attributed to a secondary order-parameter. At ultra-lowfrequency, a quasi-elastic component evidenced by Brillouin scattering and associated to the unresolvedcentral peak observed in neutron scattering, is attributed to center of mass anharmonic motions andrattling of the molecular cations in the perovskite cavities.
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Mixing-demixing transition and void formation in quasi-2D binary mixtures on a sphere
Auteur(s): Truzzolillo D.
(Article) Publié:
The Journal Of Chemical Physics, vol. 156 p.034904 (2022)
Texte intégral en Openaccess :
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Thermodynamic insights on the liquid-liquid fractionation of gluten proteins in aqueous ethanol
Auteur(s): Morel Marie-Hélène, Pincemaille J., Lecacheux Laure, Menut Paul, Ramos L., Banc A.
(Article) Publié:
Food Hydrocolloids, vol. 123 p.107142 (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03337519_v1
DOI: 10.1016/j.foodhyd.2021.107142
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Résumé: Wheat gluten includes two major proteins classes, gliadin (25–60 kg/mol) and glutenin polymers (100 to > 2,000 kg/mol) each comprising several polypeptides routinely identified by size-exclusion chromatography and electrophoresis. Gluten proteins are rich in glutamine (30%) and contain several repeated sequences, linking them to the wide class of intrinsically disordered protein (IDP). Here we showed that an ethanol/water (EtOH/W, 50/50, v/v) extract of an industrial gluten, comprising 1/3 of glutenin polymers and 2/3 of gliadin, underwent liquid-liquid phase separation (LLPS) below 14 °C, leading to two coexisting phases, respectively rich and poor in protein. As the quenching depth increased, proteins of lower and lower molecular weight joined the rich phase, akin to what would have been obtained for a polydisperse polymer sample. Within the rich phase the mass ratio of glutenin over gliadin decreased from 2.5 to 0.5 as the temperature dropped from 14 °C to −0.8 °C. Concomitantly the concentration in glutenin polymers increased up to 143 ± 6 g/L (at 9 °C) and then stopped to evolve, suggesting that the binodal line intersected the gelation line below this temperature. Applying the Flory-Huggins (FH) lattice model for each gluten protein classes, we demonstrated that their partitioning in the coexisting phases followed a same temperature dependency. However, some gliadin species joined the rich phase above their critical temperature. Here, specific interactions with the glutenin polymers through weak forces were exemplified. The study demonstrated the relevance of the Flory-Huggins (FH) lattice model in predicting phase behavior even when applied to complex protein mixtures.
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Bridging steady-state and stick-slip fracture propagation in glassy polymers
Auteur(s): Nziakou Y. K., Fischer Guillaume, George M., Bresson Bruno, Tiennot Mathilde, Roux Stéphane, Halary Jean-Louis, Ciccotti Matteo
(Article) Publié:
Soft Matter, vol. p. (2022)
Texte intégral en Openaccess :
Ref HAL: hal-03475907_v1
DOI: 10.1039/D1SM01450A
Exporter : BibTex | endNote
Résumé: Both an experimental and a theoretical investigation of the fracture propagation mechanisms acting at the process zone scale in glassy polymers are presented. The main aim is to establish a common modeling for different kinds of glassy polymers presenting either steady-state fracture propagation or stick-slip fracture propagation or both, depending on loading conditions and sample shape. On the experimental point of view, new insights are provided by in-situ AFM measurements of the viscoplastic strain fields acting within the micrometric process zone in a brittle epoxy resin, which highlight an extremely slow unexpected steadystate regime with finite plastic strains of about 30% around a blunt crack tip, and accompanied by propagating shear lips. On the theoretical point of view, we apply to glassy polymers some recently developed models for describing soft dissipative fracture that are pertinent with the observed finite strains. We propose a unified modeling of the fracture energy for both the steady-state and stick-slip fracture propagation based on the evaluation of the energy dissipation density at a characteristic strain rate induced in the process zone by the competition between the crack propagation velocity and the macroscopic sample loading rate.
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