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Production scientifique
Jamming, plasticité et défaillance des matériaux
(2) Production(s) de l'année 2024
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Water-Driven Sol–Gel Transition in Native Cellulose/1-Ethyl-3-methylimidazolium Acetate Solutions 
Auteur(s): Mohamed Yunus Roshan Akdar, Koch Marcus, Dieudonne-George P., Truzzolillo D., Colby Ralph, Parisi Daniele
(Article) Publié:
Acs Macro Letters, vol. 13 p.219-226 (2024)
Ref HAL: hal-04426657_v1
DOI: 10.1021/acsmacrolett.3c00710
Exporter : BibTex | endNote
Résumé: The addition of water to native cellulose/1-ethyl-3methylimidazolium acetate solutions catalyzes the formation of gels, where polymer chain-chain intermolecular associations act as cross-links. However, the relationship between water content (Wc), polymer concentration (Cp), and gel strength is still missing. This study provides the fundamentals to design water-induced gels. First, the sol-gel transition occurs exclusively in entangled solutions, while in unentangled ones, intramolecular associations hamper interchain cross-linking, preventing the gel formation. In entangled systems, the addition of water has a dual impact: at low water concentrations, the gel modulus is water-independent and controlled by entanglements. As water increases, more cross-links per chain than entanglements emerge, causing the modulus of the gel to scale as Gp ∼ C p^2 Wc^3.0±0.2. Immersing the solutions in water yields hydrogels with noncrystalline, aggregate-rich structures. Such water-ionic liquid exchange is examined via Raman, FTIR, and WAXS. Our findings provide avenues for designing biogels with desired rheological properties.
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A threshold model of plastic waste fragmentation: new insights into the distribution of microplastics in the ocean and its evolution over time
Auteur(s): George M., Nallet Frédéric, Fabre P.
(Article) Publié:
Marine Pollution Bulletin, vol. 199 p.116012 (2024)
Texte intégral en Openaccess : 
Ref HAL: hal-04399066_v1
Ref Arxiv: 2307.04162
DOI: 10.1016/j.marpolbul.2023.116012
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Plastic pollution in the aquatic environment has been assessed for many years by ocean waste collection expeditions around the globe or by river sampling. While the total amount of plastic produced worldwide is well documented, the amount of plastic found in the ocean, the distribution of particles on its surface and its evolution over time are still the subject of much debate. In this article, we propose a general fragmentation model, postulating the existence of a critical size below which particle fragmentation becomes extremely unlikely. In the frame of this model, an abundance peak appears for sizes around 1mm, in agreement with real environmental data. Using, in addition, a realistic exponential waste feed to the ocean, we discuss the relative impact of fragmentation and feed rates, and the temporal evolution of microplastics (MP) distribution. New conclusions on the temporal trend of MP pollution are drawn.
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