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Production scientifique
Matière Molle
(421) Articles dans des revues
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Microscopic dynamics and failure precursors of a gel under mechanical load
Auteur(s): Aime S., Ramos L., Cipelletti L.
(Article) Publié:
Proceedings Of The National Academy Of Sciences Of The United States Of America, vol. 115 p.3587 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01904079_v1
Ref Arxiv: 1804.01810
DOI: 10.1073/pnas.1717403115
WoS: 000429012500051
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
19 Citations
Résumé: Material failure is ubiquitous, with implications from geology to everyday life and material science. It often involves sudden, unpredictable events, with little or no macroscopically detectable precursors. A deeper understanding of the microscopic mechanisms eventually leading to failure is clearly required, but experiments remain scarce. Here, we show that the microscopic dynamics of a colloidal gel, a model network-forming system, exhibit dramatic changes that precede its macroscopic failure by thousands of seconds. Using an original setup coupling light scattering and rheology, we simultaneously measure the macroscopic deformation and the microscopic dynamics of the gel, while applying a constant shear stress. We show that the network failure is preceded by qualitative and quantitative changes of the dynamics, from reversible particle displacements to a burst of irreversible plastic rearrangements.
Commentaires: . Réf Journal: PNAS 115, 3587 (2018)
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Nano-porous structures via self-assembly of amphiphilic triblock copolymers: influence of solvent and molecular weight
Auteur(s): Nehache Sabrina, Semsarilar M., In M., Dieudonne-George P., Lai Kee Him J., Bron P., Quemener D.
(Article) Publié:
Journal Of Polymer Science Part A: Polymer Chemistry, vol. 9 p.193-202 (2018)
Ref HAL: hal-01680368_v1
DOI: 10.1039/c7py01853c
WoS: 000418645100006
Exporter : BibTex | endNote
4 Citations
Résumé: Control of film structures made from a polystyrene-polystyrene sodium sulfonate-polystyrene (PS-PNaSS-PS) copolymer micellar solution is investigated in a THF/water mixture. Four different copolymers (varying molecular weights) are synthesised via RAFT (Reversible Addition Fragmentation chain Transfer) polymerisation. Depending on parameters such as copolymer molecular weight, solvent composition and copolymer concentration, the PS-PNaSS-PS triblock self-assembles into different morphologies in solution and dry state. The effect of each parameter is investigated using characterization techniques such as AFM, TEM, Cryo-TEM, SEM and SAXS. The morphologies obtained for PS-PNaSS-PS are found to be extremely sensitive when the water content of the micellar solution is low. Among the structures observed, a highly ordered nano-porous film is obtained using a PS10k-PNaSS6k-PS10k triblock copolymer solution containing 3.0 wt% of water. This micellar solution is used to prepare a porous membrane for filtration applications. Pure water filtration data suggest a pore size in the range of ultrafiltration, making these membranes attractive for applications in the food industry, for bacteria, virus and protein removal.
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Phase transitions in polymorphic materials probed using space-resolved diffusing wave spectroscopy
Auteur(s): Nagazi M. Y., Dieudonne-George P., Brambilla G., Meunier Gerard, Cipelletti L.
(Article) Publié:
Soft Matter, vol. 14 p.6439-6448 (2018)
Ref HAL: hal-01896690_v1
DOI: 10.1039/c8sm00911b
WoS: WOS:000442269000021
Exporter : BibTex | endNote
1 Citation
Résumé: We use space-resolved dynamic light scattering in the highly multiple scattering regime (Photon Correlation Imaging Diffusing Wave Spectroscopy, PCI-DWS) to investigate temperature-induced phase transitions in polymorphic materials. We study paraffin wax as a simple model system and chocolate, a prototypical example of fat-based products exhibiting complex, history-dependent phase transitions. We find that microscopic dynamics measured using PCI-DWS show remarkable, non-monotonic behavior upon heating: they transiently accelerate when crossing phase transition and slow down above the transition temperature. Sub-micron resolution measurements of the local drift of the sample surface reveal that the speed-up of the dynamics is due to the strain field induced by the change in density at transition temperature. The transition temperatures obtained from PCI-DWS are found to be in excellent agreement with those inferred from complementary differential scanning calorimetry and X-ray scattering experiments, thereby validating PCI-DWS as a new, powerful tool for the characterization of phase transitions in complex soft matter. Finally, we demonstrate the unique possibilities afforded by space-resolved DWS by investigating the spatially heterogeneous response of poorly manufactured or composite chocolate samples.
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Glass transition of soft colloids
Auteur(s): Philippe A. M., Truzzolillo D., Galvan-myoshi Julian, Dieudonne-George P., Trappe Veronique, Berthier L., Cipelletti L.
(Article) Publié:
Physical Review E, vol. 97 p.040601 (2018)
PMID 29758608
DOI: 10.1103/PhysRevE.97.040601
WoS: WOS:000429636700001
30 Citations
Résumé: We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τα of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τα on approaching the glass transition is independent of particle softness. By contrast, softness becomes relevant at very large packing fractions when the system falls out of equilibrium. In this nonequilibrium regime, τα depends surprisingly weakly on packing fraction, and time correlation functions exhibit a compressed exponential decay consistent with stress-driven relaxation. The transition to this novel regime coincides with the onset of an anomalous decrease in local order with increasing density typical of ultrasoft systems. We propose that these peculiar dynamics results from the combination of the nonequilibrium aging dynamics expected in the glassy state and the tendency of colloids interacting through soft potentials to refluidize at high packing fractions.
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Power law viscoelasticity of a fractal colloidal gel
Auteur(s): Aime S., Cipelletti L., Ramos L.
(Article) Publié:
Journal Of Rheology / Transactions Of The Society Of Rheology; Society Of Rheology -- Transactions, vol. 62 p.1429-1441 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01889803_v1
Ref Arxiv: 1802.03820
DOI: 10.1122/1.5025622
WoS: 000449684700010
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
10 Citations
Résumé: Power law rheology is of widespread occurrence in complex materials that are characterized by the presence of a very broad range of microstructural length and time scales. Although phenomenological models able to reproduce the observed rheological features exist, in general a well-established connection with the microscopic origin of this mechanical behavior is still missing. As a model system, this work focuses on a fractal colloidal gel. We thoroughly characterize the linear power law rheology of the sample and its age dependence. We show that at all sample ages and for a variety of rheological tests the gel linear viscoelasticity is very accurately described by a Fractional Maxwell (FM) model, characterized by a power law behavior. Thanks to a unique set-up that couples small-angle static and dynamic light scattering to rheological measurements, we demonstrate that the power law rheology observed in the linear regime originates from reversible non-affine rearrangements and discuss the possible relationship between the FM model and the microscopic structure of the gel.
Commentaires: . Réf Journal: Journal of Rheology, 62, 1429-1441 (2018)
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Kinetic regimes in the curing process of epoxy-phenol composites
Auteur(s): Granado Lérys, Kempa Stefan, Gregoriades Laurence, Brüning Frank, Genix A.-C., Fréty Nicole, Anglaret E.
(Article) Publié:
Thermochimica Acta, vol. 667 p.185 - 192 (2018)
Ref HAL: hal-01881804_v1
DOI: 10.1016/j.tca.2018.07.019
WoS: 000444663600024
Exporter : BibTex | endNote
9 Citations
Résumé: Despite an abundant literature on epoxy-amine systems, a complete description of the curing kinetics in epoxy-phenol composites was still lacking. In this study, the curing kinetics of an epoxy-phenol composite relevant to microelectronics industry is probed by isothermal and non-isothermal differential scanning calorimetry. An isoconversional analysis of the data reveals a significant contribution of the diffusion of molecular species to the activation energy, at low temperature and high degrees of curing. A model-fitting of the kinetics is performed in two successive steps: high-temperatures data are fitted with Arrhenius law and nth order autocatalytic model (where the diffusion contribution is neglected), whereas low-temperature data are fitted using Rabinowitch and modified-Williams-Landel-Ferry models (considering a diffusion contribution related to the glass transition). The chemical and diffusion contributions to the rate constants are calculated at various temperatures, clarifying the kinetics regimes with precision. Finally, the kinetics regimes are summarized in an improved time-temperature-transformation diagram.
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On the effect of local sample slope during modulus measurements by contact-resonance atomic force microscopy
Auteur(s): Heinze K., Arnould Olivier, Delenne Jean-Yves, Lullien-Pellerin V., Ramonda M., George M.
(Article) Publié:
Ultramicroscopy, vol. 194 p.78 - 88 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01869770_v1
DOI: 10.1016/j.ultramic.2018.07.009
WoS: 000450281700010
Exporter : BibTex | endNote
1 Citation
Résumé: Contact-resonance atomic force microscopy (CR-AFM) is of great interest and very valuable for a deeper understanding of the mechanics of biological materials with moduli of at least a few GPa. However, sample surfaces can present a high topography range with significant slopes, where the local angle can be as large as ± 50°. The non-trivial correlation between surface slope and CR-frequency hinders a straightforward interpretation of CR-AFM indentation modulus measurements on such samples. We aim to demonstrate the significant influence of the surface slope on the CR-frequency that is caused by the local angle between sample surface and the AFM cantilever and present a practical method to correct the measurements. Based on existing analytical models of the effect of the AFM set-up's intrinsic cantilever tilt on CR-frequencies, we compute the non-linear variation of the first two (eigen)modes CR-frequency for a large range of surface angles. The computations are confirmed by CR-AFM experiments performed on a curved surface. Finally, the model is applied to directly correct contact modulus measurements on a durum wheat starch granule as an exemplary sample.
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