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Recent advances in biosurfactant-based association colloids—Self-assembly in water
Auteur(s): Hellweg Thomas, Sottmann Thomas, Oberdisse J.
(Article) Publié:
Frontiers In Soft Matter, vol. 2 p. (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04389124_v1
DOI: 10.3389/frsfm.2022.1081877
Exporter : BibTex | endNote
Résumé: Recent studies of self-assembly in binary systems of bio-surfactants, either of microbial origin or saponins extracted from plants, are reviewed. Saponins in water reported in the first section include aescin, glycyrrhizin, and quillaja saponins, while rhamnolipids are discussed in the second section on microbial surfactants. Studies of surface activities are a natural starting point of the characterization of surfactants, but here we focus mainly on physico-chemical and structural properties of self-assembled bulk structures in solution, often characterized by scattering techniques. When quantitative modelling is performed, self-assembly parameters like aggregation numbers, head group areas, and resulting shapes can be followed as a function of physical-chemical parameters like concentration, composition, temperature, or pH. Morphologies include micelles and their structural evolution with addition of other bio- or synthetic surfactants, co-surfactants, proteins or phospholipids.
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On the absence of structure factors in concentrated colloidal suspensions and nanocomposites
Auteur(s): Genix A.-C., Oberdisse J.
(Article) Publié:
European Physical Journal E, vol. 46 p.46 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04244864_v1
Ref Arxiv: 2310.14682
DOI: 10.1140/epje/s10189-023-00306-6
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Small-angle scattering is a commonly used tool to analyze the dispersion of nanoparticles in all kinds of matrices. Besides some obvious cases, the associated structure factor is often complex and cannot be reduced to a simple interparticle interaction, like excluded volume only. In recent experiments, we have encountered a surprising absence of structure factors (S(q) = 1) in scattering from rather concentrated polymer nanocomposites [A.-C. Genix et al, ACS Appl. Mater. Interfaces 11 (2019) 17863]. In this case, quite pure form factor scattering is observed. This somewhat “ideal” structure is further investigated here making use of reverse Monte Carlo simulations in order to shed light on the corresponding nanoparticle structure in space. By fixing the target “experimental” apparent structure factor to one over a given q-range in these simulations, we show that it is possible to find dispersions with this property. The influence of nanoparticle volume fraction and polydispersity has been investigated, and it was found that for high concentrations only a high polydispersity allows reaching a state of S = 1. The underlying structure in real space is discussed in terms of the pair-correlation function, which evidences the importance of attractive interactions between polydisperse nanoparticles. The calculation of partial structure factors shows that there is no specific ordering of large or small particles, but that the presence of attractive interactions together with polydispersity allows reaching an almost “structureless” state.
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Mini review: recent advances in biosurfactant-based association colloids–formation of microemulsions
Auteur(s): Hellweg Thomas, Sottmann Thomas, Oberdisse J.
(Article) Publié:
Frontiers In Soft Matter, vol. 3 p.1260211 (2023)
Ref HAL: hal-04244898_v1
DOI: 10.3389/frsfm.2023.1260211
Exporter : BibTex | endNote
Résumé: In the context of a more sustainable economy, bio-surfactants become increasingly important, due to their independence of petrol-based chemistry, their usually mild synthesis conditions, and in certain cases their pharmacological activity. We have recently discussed self-assembly studies in binary systems of bio-surfactants of microbial origin, or saponins extracted from plants (Hellweg et al., Frontiers in Soft Matter, 2023, 2). In the present review, we focus on the formation of microemulsions based on these molecules. We review the formation and structure of microemulsion systems formed by oil, water, and biosurfactants, with a particular focus on Quillaja saponins and rhamnolipids.
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Editorial: Nanocomposites with interfaces controlled by grafted or adsorbed polymers
Auteur(s): Holderer O., Genix A.-C., Kruteva M., Oberdisse J.
(Article) Publié:
Frontiers In Physics, vol. 10 p.1117549 (2023)
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How Tuning Interfaces Impacts the Dynamics and Structure of Polymer Nanocomposites Simultaneously
Auteur(s): Genix A.-C., Bocharova Vera, Carroll Bobby, Dieudonne-George P., Chauveau E., Sokolov Alexei, Oberdisse J.
(Article) Publié:
Acs Appl. Mater. Interfaces, vol. 15 p.7496-7510 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04244949_v1
Ref Arxiv: 2310.14680
DOI: 10.1021/acsami.2c18083
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Fundamental understanding of macroscopic properties of polymer nanocomposites (PNCs) remains difficult due to the complex interplay of microscopic dynamics and structure, namely interfacial layer relaxations and three-dimensional nanoparticle arrangements. The effect of surface modification by alkyl methoxysilanes at different grafting densities has been studied in PNCs made of poly(2-vinylpyridine) and spherical 20 nm silica nanoparticles (NPs). The segmental dynamics has been probed by broadband dielectric spectroscopy, and the filler structure by small-angle X-ray scattering and reverse Monte Carlo simulations. By combining the particle configurations with the interfacial layer properties, it is shown how surface modification tunes the attractive polymer-particle interactions: bare NPs slow down the polymer interfacial layer dynamics over a thickness of ca. 5 nm, while grafting screens these interactions. Our analysis of interparticle spacing and segmental dynamics provides unprecedented insight into the effect of surface modification on the main characteristics of PNCs: particle interactions and polymer interfacial layers.
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Influence of the Graft Length on Nanocomposite Structure and Interfacial Dynamics
Auteur(s): Genix A.-C., Bocharova Vera, Carroll Bobby, Dieudonne-George P., Chauveau E., Sokolov Alexei, Oberdisse J.
(Article) Publié:
Nanomaterials, vol. 13 p.748 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04244883_v1
Ref Arxiv: 2310.11201
DOI: 10.3390/nano13040748
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Both the dispersion state of nanoparticles (NPs) within polymer nanocomposites (PNCs) and the dynamical state of the polymer altered by the presence of the NP/polymer interfaces have a strong impact on the macroscopic properties of PNCs. In particular, mechanical properties are strongly affected by percolation of hard phases, which may be NP networks, dynamically modified polymer regions, or combinations of both. In this article, the impact on dispersion and dynamics of surface modification of the NPs by short monomethoxysilanes with eight carbons in the alkyl part (C8) is studied. As a function of grafting density and particle content, polymer dynamics is followed by broadband dielectric spectroscopy and analyzed by an interfacial layer model, whereas the particle dispersion is investigated by small-angle X-ray scattering and analyzed by reverse Monte Carlo simulations. NP dispersions are found to be destabilized only at the highest grafting. The interfacial layer formalism allows the clear identification of the volume fraction of interfacial polymer, with its characteristic time. The strongest dynamical slow-down in the polymer is found for unmodified NPs, while grafting weakens this effect progressively. The combination of all three techniques enables a unique measurement of the true thickness of the interfacial layer, which is ca. 5 nm. Finally, the comparison between longer (C18) and shorter (C8) grafts provides unprecedented insight into the efficacy and tunability of surface modification. It is shown that C8-grafting allows for a more progressive tuning, which goes beyond a pure mass effect.
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Recent scattering approaches to structure and dynamics of polymer nanocomposites
Auteur(s): Kruteva M., Genix A.-C., Holderer O., Oberdisse J.
(Article) Publié:
Frontiers In Soft Matter, vol. 2 p.992563 (2022)
Ref HAL: hal-04244916_v1
DOI: 10.3389/frsfm.2022.992563
Exporter : BibTex | endNote
Résumé: The characterization of polymer nanocomposites on molecular length scales and timescales is a challenging task, which is also indispensable for the understanding of macroscopic material's properties. Neutron scattering is one of the techniques which are very well-suited for studying the structure and molecular motion in such soft matter systems. X-rays can also be used for the same purpose, however, with higher energy and thus a different focus on dynamics, where they are better suited for nanoparticle motion. In this mini-review, we aim at highlighting recent results in the field of polymer nanocomposites, including nanoparticle structure in various experimental systems, from model to industrial, and polymer and particle dynamics. This allows establishing the link between microscopic and macroscopic properties, in particular rheology.
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