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(24) Production(s) de l'année 2023
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Discussion about suitable applications for biodegradable plastics regarding their sources, uses and end of life
Auteur(s): Paul-Pont Ika, Ghiglione Jean-François, Gastaldi Emmanuelle, ter Halle Alexandra, Huvet Arnaud, Bruzaud Stéphane, Lagarde Fabienne, Galgani François, Duflos Guillaume, George M., Fabre P.
(Article) Publié:
Waste Management, vol. 157 p.242-248 (2023)
Ref HAL: hal-04186887_v1
PMID 36577275
DOI: 10.1016/j.wasman.2022.12.022
WoS: 000972939800001
Exporter : BibTex | endNote
Résumé: This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels.
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Structure and elasticity of model disordered, polydisperse, and defect-free polymer networks
Auteur(s): Sorichetti V., Ninarello A. S., Ruiz-Franco José, Hugouvieux Virginie, Zaccarelli Emanuela, Micheletti Cristian, Kob W., Rovigatti Lorenzo
(Article) Publié:
The Journal Of Chemical Physics, vol. 158 p.074905 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04043309_v1
Ref Arxiv: 2211.04810
DOI: 10.1063/5.0134271
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: The elasticity of disordered and polydisperse polymer networks is a fundamental problem of soft matter physics that is still open. Here, we self-assemble polymer networks via simulations of a mixture of bivalent and tri- or tetravalent patchy particles, which result in an exponential strand length distribution analogous to that of experimental randomly cross-linked systems. After assembly, the network connectivity and topology are frozen and the resulting system is characterized. We find that the fractal structure of the network depends on the number density at which the assembly has been carried out, but that systems with the same mean valence and same assembly density have the same structural properties. Moreover, we compute the long-time limit of the mean-squared displacement, also known as the (squared) localization length, of the cross-links and of the middle monomers of the strands, showing that the dynamics of long strands is well described by the tube model. Finally, we find a relation connecting these two localization lengths at high density and connect the cross-link localization length to the shear modulus of the system.
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Hidden traces of chirality in the fluctuations of a fully unwound cholesteric
Auteur(s): Poy G.
(Article) Publié:
Soft Matter, vol. 19 p.1115-1130 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-03953472_v1
DOI: 10.1039/D2SM01646J
Exporter : BibTex | endNote
Résumé: Confinement and hydrodynamic interactions often play an important role in the fluctuation dynamics of soft matter systems, which can typically be studied using light scattering techniques. With experimental and theoretical methodologies, I demonstrate here that chirality is an additional critical parameter that leads to diverging decay times and correlation lengths in chiral liquid crystal cells with a fully unwound cholesteric helix. This study combines light scattering measurements made in a tailored microscope geometry and theoretical calculations of the decay dynamics of chiral orientational fluctuations---including hydrodynamics---to establish the existence of two soft chiral modes of fluctuations driving the destabilization of the unwound cholesteric. Despite the achirality of the equilibrium state of unwound cholesterics, this study indicates that chirality hides itself in the orientational fluctuation modes and plays a major role in their dynamics, which can be exploited to locally measure the strength of chirality in frustrated chiral liquid crystal cells.
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