Metal oxide aluminosilicate and aluminogermanate nanotubes, called imogolite nanotubes, are custom made nanotubes with controlled diameter, morphology and organization. These nanotubes undergo major structural changes at high temperatures. Here, we report a complete analysis of the structural transformation of single and double-walled aluminogermanate nanotubes, organized or not in bundles, up to 800 • C. Complementary X-ray scattering and spectroscopy experiments were performed. The evolution of both Al and Ge atoms coordination during the transformation process was studied in-situ. Quantitative analysis of X-ray absorption spectra reveals that the dehydroxylation of nanotubes leads to intermediate stages of 'metaimogolite', which differ in the coordination of the aluminium atoms. A mechanism explaining the major structural reorganization is proposed based on atomic jump processes.

The liquid mixing process is an advantageous production method which has recently gained industrial interest for elaborating composites based on natural rubber (NR) and filler nanoparticles (NPs). Understanding how the relevant components such as polymer, fillers, as well as proteins and lipids coming from NR organize along the fabrication process is of importance for modulating material properties. Here, we successfully employed a combination of nano-imaging techniques to unravel the structure and evolution of hetero-aggregates formed by colloidal destabilization of a model NR latex - silica NPs liquid mixing process. First, field emission scanning electron microscopy (FESEM) was used to investigate the structures, from the early stage of contact between the particles until the formation of a composite. Results highlight an interaction in the liquid state between NR globules contained within the latex and silica NPs, hindering coalescence among globules. The latter can be achieved by applying shear in suspension or by solvent evaporation obtaining a dried composite. Atomic force microscopy coupled to infrared spectroscopy (AFM-IR) was employed to probe the in-depth nanoscopic distribution of silica NPs revealing a restricted mobility of the NPs during evaporation. Ultimately, the spatial distribution of proteins and lipids of NR, with respect to silica NPs, was investigated using dual color fluorescence images acquired with direct stochastic optical reconstruction microscopy (d-STORM) in a correlative light electron microscopy (CLEM) approach. The presence of silica NPs is found to influence the distribution of proteins and lipids in the composite; biomolecules form clusters of ~200 nm, which are partially colocalized with silica, highlighting an interaction between them. Our work provides comprehensive structural understanding of a model system undergoing liquid mixing, unlocking the potential of combining high-resolution imaging techniques to elucidate the structure of materials for tire applications.

Rubber-based nanocomposites prepared by solid-phase mixing with precipitated silica nanoparticlesare typically strongly aggregated systems with different levels of spatial organization. The strategy thatwe developed several years ago to investigate such systems is based on the study of simplifiedindustrial samples with ingredients limited to a strict minimum. On the scale of a micrometricsimulation box, tens of thousands of nanoparticles are embedded in the matrix, and their dispersionstrongly affects the mechanical properties of the material – and which is reflected in the scatteredintensity. A statistical method based on a reverse Monte Carlo solution of this many-parameterproblem will be presented, showing that some key features like percolation can be described. [1]Another key feature of rubber nanocomposites refers to the influence of the filler surfaces on thepolymer dynamics, and some recent progress – including incoherent neutron spin-echo measurements– will be discussed. [2] Such results may be confronted to dielectric spectroscopy measurements whichin some cases are not conclusive due the impossibility to correctly resolve the α-relaxation in presenceof strong interfacial polarization processes. An original application of dielectric spectroscopy with asurprising measurement of the adsorption isotherm of coating agents onto silica buried in the polymermatrix will also be discussed. [3][1] Musino D, Genix A-C, Chauveau E, Bizien T, Oberdisse J, Nanoscale 2020, 12:3907.[2] Musino D, Oberdisse J, Farago B, Alegria A, Genix A-C, ACS Macro Letters 2020, 9:910.[3] Musino D, Oberdisse J, Sztucki M, Alegria A, Genix A-C, Macromolecules 2020, 53:8083.

Polymerized ionic liquids (PolyILs) are an emerging class of polymer electrolytes which offer solutions to many problems in current battery technology. They combine the attractive features of ionic liquids with the mechanical strength of polymeric materials. However, a major obstacle in use of dry PolyILs is their low ionic conductivity at ambient temperature, which remains below the level required for many applications (ca. 10-3 S/cm). In this context, it has been shown that a significant enhancement of the ionic conductivity can be obtained by decoupling the ion motion from the segmental dynamics in polymers. We will review recent results obtained in this field using broadband dielectric spectroscopy, and discuss the microscopic parameters controlling ionic conductivity in PolyILs below Tg [1]. In particular, our detailed study of imidazolium-based PolyILs helped to unravel the interplay between nanostructure and ion conduction mechanism [2]. We also report first quasi-elastic neutron scattering experiments in these polymers suggesting the role of fast dynamics in assisting ion transport in the glassy state [3].[1] V. Bocharova and A.P. Sokolov, Macromolecules 2020, 53, 4141.[2] B. Doughty, A.C. Genix, I. Popov, B. Li, S. Zhao, T. Saito, D. Lutterman, R. Sacci, B.G. Sumpter, Z. Wojnarowska, V. Bocharova, Phys. Chem. Chem. Phys. 2019, 21, 14775.[3] V. Bocharova, A.C. Genix, A. Kisliuk, G. Sala, N.C. Osti, E. Mamontov, A. P. Sokolov, J. Phys. Chem. B 2020, 124, 10539.

The highest quality hexagonal boron nitride (hBN) crystals are grown from molten solutions. For hBN crystal growth at atmospheric pressure, typically the solvent is a combination of two metals, one with a high boron solubility and the other to promote nitrogen solubility. In this study, we demonstrate that high-quality hBN crystals can be grown at atmospheric pressure using pure iron as a flux. The ability to produce excellent-quality hBN crystals using pure iron as a solvent is unexpected, given its low solubility for nitrogen. The properties of crystals produced with this flux matched the best values ever reported for hBN: a narrow Raman E2g vibration peak (7.6 cm–1) and strong phonon-assisted peaks in the photoluminescence spectra. To further test their quality, the hBN crytals were used as a substrate for WSe2 epitaxy. WSe2 was deposited with a low nucleation density, indicating the low defect density of the hBN. Lastly, the carrier tunneling through our hBN thin layers (3.5 nm) follows the Fowler–Nordheim model, with a barrier height of 3.7 eV, demonstrating hBN’s superior electrical insulating properties. This ability to produce high-quality hBN crystals in such a simple, environmentally friendly and economical process will advance two-dimensional material research by enabling integrated devices.

Les méthodes expérimentales permettant de détecter la résonance de spin électronique de défauts ponctuels du diamant ouvrent de nouvelles perspectives pour le développement de capteurs quantiques à haute sensibilité. De tels capteurs ont notamment démontré des performances exceptionnelles pour l’imagerie magnétique aux échelles nanométriques, conduisant à une transition accélérée vers des solutions commerciales.