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(10) Production(s) de l'année 2020
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Polypyrrole nanostructures modified with mono- and bimetallic nanoparticles for photocatalytic H2 generation
Auteur(s): Yuan Xiaojiao, Dragoe Diana, Beaunier Patricia, Uribe Daniel Bahena, Ramos L., Méndez-Medrano Maria Guadalupe, Remita Hynd
(Article) Publié:
Journal Of Materials Chemistry A, vol. 8 p.268-277 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03437340_v1
DOI: 10.1039/C9TA11088G
Exporter : BibTex | endNote
Résumé: Conjugated polymer polypyrrole nanostructures modified with bimetallic (Pt–Ni) nanoparticles are very active for hydrogen generation and a synergetic effect is obtained by alloying Pt with Ni.
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Role of Normal Stress in the Creep Dynamics and Failure of a Biopolymer Gel
Auteur(s): Pommella A., Cipelletti L., Ramos L.
(Article) Publié:
Physical Review Letters, vol. 125 p.268006 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03139495_v1
DOI: 10.1103/PhysRevLett.125.268006
WoS: WOS:000604249900023
Exporter : BibTex | endNote
Résumé: We investigate the delayed rupture of biopolymer gels under a constant shear load by simultaneous dynamic light scattering and rheology measurements. We unveil the crucial role of normal stresses built up during gelation: All samples that eventually fracture self-weaken during the gelation process, as revealed by a partial relaxation of the normal stress concomitant to a burst of microscopic plastic rearrangements.Upon applying a shear stress, weakened gels exhibit in the creep regime distinctive signatures in their microscopic dynamics, which anticipate macroscopic fracture by up to thousands of seconds. The dynamics in fracturing gels are faster than those of nonfracturing gels and exhibit large spatiotemporal fluctuations. A spatially localized region with significant plasticity eventually nucleates, expands progressively, and finally invades the whole sample, triggering macroscopic failure.
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Role of normal stress in the creep dynamics and failure of a biopolymer gel
Auteur(s): Pommella A., Cipelletti L., Ramos L.
(Document sans référence bibliographique) 2020-12-17Texte intégral en Openaccess :
Ref HAL: hal-03081334_v1
Ref Arxiv: 2012.09827
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We investigate the delayed rupture of biopolymer gels under a constant shear load by simultaneous dynamic light scattering and rheology measurements. We unveil the crucial role of normal stresses built up during gelation: all samples that eventually fracture self-weaken during the gelation process, as revealed by a partial relaxation of the normal stress concomitant to a burst of microscopic plastic rearrangements. Upon applying a shear stress, weakened gels exhibit in the creep regime distinctive signatures in their microscopic dynamics, which anticipate macroscopic fracture by up to thousands of seconds. The dynamics in fracturing gels are faster than those of non-fracturing gels and exhibit large spatio-temporal fluctuations. A spatially localized region with significant plasticity eventually nucleates, expands progressively, and finally invades the whole sample triggering macroscopic failure.
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Rejuvenating the structure and rheological properties of silica nanocomposites based on natural rubber
Auteur(s): Boonsomwong Kanyarat, Genix A.-C., Chauveau E., Fromental J.-M., Dieudonne-George P., Sirisinha Chakrit, Oberdisse J.
(Article) Publié:
Polymer, vol. 189 p.122168 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03004917_v1
Ref Arxiv: 2011.07820
DOI: 10.1016/j.polymer.2020.122168
WoS: WOS:000513011400007
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: The antagonistic effect of processing and thermal annealing on both the filler structure and the polymer matrix is explored in polymer nanocomposites based on natural rubber with precipitated silica incorporated by coagulation from aqueous suspension followed by roll-milling. Their structure and linear and non-linear rheology have been studied, with a particular emphasis on the effect of high temperature thermal treatment and the number of milling passes. Small-angle X-ray scattering intensities show that the silica is organized in small, unbreakable aggregates containing ca. 50 primary nanoparticles, which are reorganized on a larger scale in filler networks percolating at the highest silica contents. As expected, the filler network structure is found to be sensitive to milling, more milling inducing rupture, as evidenced by the decreasing Payne effect. After thermal treatment, the nanocomposite structure is found to be rejuvenated, erasing the effect of the previous milling on the low-strain modulus. In parallel, the dynamics of the samples described by the rheology or the calorimetric glass-transition temperature remain unchanged, whereas the natural latex polymer network structure is modified by milling towards a more fluid-like rheology, and cannot be recovered.
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Tailoring the viscoelasticity of polymer gels of gluten proteins through solvent quality
Auteur(s): Costanzo S., Banc A., Louhichi A., Chauveau E., Wu Baohu, Morel Marie-Hélène, Ramos L.
(Article) Publié:
Macromolecules, vol. 53 p.9470-9479 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03003151_v1
Ref Arxiv: 2010.10317
DOI: 10.1021/acs.macromol.0c01466
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We investigate the linear viscoelasticity of polymer gels produced by the dispersion of gluten proteins in water:ethanol binary mixtures with various ethanol contents, from pure water to 60% v/v ethanol. We show that the complex viscoelasticity of the gels exhibits a time/solvent composition superposition principle, demonstrating the self-similarity of the gels produced in different binary solvents. All gels can be regarded as near critical gels with characteristic rheological parameters, elastic plateau and characteristic relaxation time, which are related one to another, as a consequence of self-similarity, and span several orders of magnitude when changing the solvent composition. Thanks to calorimetry and neutron scattering experiments, we evidencea co-solvency effect with a better solvation of the complex polymer-like chains of the gluten proteins as the amount of ethanol increases. Overall the gel viscoelasticity can be accounted for by a unique characteristic length characterizing the crosslink density of the supramolecular network, which is solvent composition-dependent. On a molecular level, these findings could be interpreted as a transition of the supramolecular interactions, mainly H-bonds, from intra- to interchains, which would be facilitated by the disruption of hydrophobic interactions by ethanol molecules. This work provides new insight for tailoring the gelation process of complex polymer gels.
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Spinning elastic beads: a route for simultaneous measurements of the shear modulus and the interfacial energy of soft materials
Auteur(s): Carbonaro A., Chagua-Encarnacion Kennedy-Nexon, Charles C.-A., Phou T., Ligoure C., Mora S., Truzzolillo D.
(Article) Publié:
Soft Matter, vol. 16 p.8412 - 8421 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02947316_v1
DOI: 10.1039/d0sm01024c
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Résumé: Large deformations of soft elastic beads spinning at high angular velocity in a denser background fluid are investigated theoretically, numerically, and experimentally using millimeter-size polyacry-lamide hydrogel particles introduced in a spinning drop tensiometer. We determine the equilibrium shapes of the beads from the competition between the centrifugal force and the restoring elastic and surface forces. Considering the beads as neo-Hookean up to large deformations, we show that their elastic modulus and surface energy constant can be simultaneously deduced from their equilibrium shape. Also, our results provide further support to the scenario in which surface energy and surface tension coincide for amorphous polymer gels.
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Ultralow effective interfacial tension between miscible molecular fluids
Auteur(s): Carbonaro A., Cipelletti L., Truzzolillo D.
(Article) Publié:
Physical Review Fluids, vol. 5 p.074001 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02912991_v1
DOI: 10.1103/PhysRevFluids.5.074001
WoS: WOS:000547338700003
Exporter : BibTex | endNote
Résumé: We exploit the deformation of drops spinning in a denser background fluid to investigate the effective interfacial tension (EIT) between miscible molecular fluids. We find that, for sufficiently low interfacial tension, spinning drops develop dumbbell shapes, with two large heads connected by a thinner central body. We show that this shape depends not only on the density and viscosity contrast between the drop and background fluids, but also on the fluid molecular structure, and hence on the stresses developing at their interface due to a different molecular interaction. We systematically investigate the dynamics of dumbbell-shaped drops of water-glycerol mixtures spinning in a pure glycerol reservoir. By developing a model for the deformation based on the balance of the shear stress opposing the deformation, the imposed normal stress on the drop, and an effective interfacial tension, we exploit the time evolution of the drop shape to measure the EIT. Our results showthat the EIT in water-glycerol systems is orders of magnitude lower than that reported in previous experimental measurements, and in excellent agreement with values calculated via the phase field model proposed by Truzzolillo et al. [Phys. Rev. X 6, 041057 (2016)].
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