Ionic liquids (ILs) are versatile solvents for a wide range of substances, including alkali and alkaline earth salts. Mixtures of ILs and these salts are promising electrolytes for Li and post-Li batteries, offering unique properties such as stability and viscosity. These characteristics stem from the multiscale coupling between structural and dynamical aspects of ILs. We focus in this study on a family of electrolytes based on the iconic IL 1-butyl-3-methylimidazolium trifluoromethylsulfonimide (BMImTFSI), in which alkali (Li+, Na+, K+, Cs+) and alkaline earth (Mg2+) TFSI salts are dissolved. First, we demonstrate how classical molecular dynamics (MD) allows reproducing structural scattering features and self-diffusion coefficients, as measured by wide angle X-ray scattering and pulsed field gradient NMR. With this approach, we show that MD also helps to decipher the subtle differences between electrolytes in which alkali or earth alkaline ions are dissolved. Second, molecular dynamics analyses based on a single particle tracking strategy allows unravelling the correlations between structural and dynamical heterogeneities in a multiscale approach (from coordination spheres/fs to nanosegregation/hundreds of ns), therefore evidencing a large distribution of dynamics and the presence of clusters with long lifetime. All these results sort out time/temperature equivalence, which appears as a key to understand the behavior of nanostructured fluids.

Polymer blends in thin films offer versatile opportunities for tailoring material properties. Among available deposition methods, the Langmuir film technique enables the formation of well-controlled nanometer-thick films at the air-water interface, revealing unique miscibility and phase behaviors not observed in bulk. In this work, we investigate 2D polymer blends composed of amphiphilic PEO11-PPO35-PEO11 and hydrophobic PDMS using a multiscale approach that combines surface pressure-area isotherms, Brewster angle microscopy (BAM), neutron reflectometry (NR), and sum-frequency generation (SFG) spectroscopy. This methodology enabled us to construct a 2D surface pressure-composition phase diagram, identifying miscibility regions and two distinct first-order phase transitions. Across all compositions, no lateral phase separation was observed at the mesoscopic scale by BAM, even during phase transitions. Instead, NR revealed vertical segregation at specific surface pressures and compositions. In PEO11-PPO35-PEO11-rich blends, a homogeneous monolayer undergoes a transition to a bilayer, with hydrophobic PDMS positioned atop PEO11-PPO35-PEO11. PDMS-rich blends display a similar bilayer structure at all pressures, with the phase transition mainly involving thickening of the PDMS layer, as seen in pure PDMS films. SFG spectroscopy reveals that both polymers have distinct behavior in the blends and in pure films, due to either lateral or vertical interactions. Notably, despite their contrasting hydrophobicities, the polymers exhibit miscibility over a range of compositions and surface pressures, with evidence of attractive interactions. These findings underscore the unique behavior of confined polymer blends and the importance of 2D-specific phase diagrams for designing functional interfacial materials.

HYPOTHESIS:We have recently shown that mixing green fatty acid 12-hydroxystearic acid (12-HSA) molecules with a low amount of various end-capped polyethylene glycol (PEG) chains (mono- or di-functionalized by 12-HSA or stearic acid (SA) moieties) provides a straightforward one-pot route to design PEGylated self-assemblies, either vesicles or multilamellar tubes. Tuning the concentration of end-capped PEG chains offers a simple strategy to precisely control the morphology of these PEGylated architectures. EXPERIMENTAL:Four types of 4 kDa end-capped PEG chains, functionalized at one or both ends with either 12-HSA or SA, were mixed with 12-HSA over a wide range of ratios between PEG-borne fatty acid moieties and free 12-HSA molecules. The detailed structure of the resulting self-assemblies was investigated by Small-Angle Neutron Scattering with contrast variation at 20 °C and 45 °C. FINDINGS:For both mono-functionalized PEGs, PEGylated multilamellar tubes are obtained, with a PEG brush density controlled by polymer content. Di-functionalized 12-HSA PEG chains yield PEGylated unilamellar vesicles whose diameter decreases with increasing PEG concentration due to curvature changes. Di-functionalized SA PEG chains form PEGylated multilamellar tubes coexisting with telechelic polymer flowers located within the interlayer at low PEG content and both inside and outside the tubes at higher concentrations. All architectures transform into small PEGylated ellipsoidal micelles between 20 and 45 °C. This dual control over structure and dimensions provides a versatile platform for designing nanocarriers adapted to specific drug-delivery requirements.

Glucuronoxylans are known to be only partly soluble in aqueous media. Chemical modification often aims to improve solubility, yet observations of aggregation even of the modified xylans are not uncommon. We investigated the aggregation of glucuronoxylans of two different molar masses (XS and XM with Mw = 14 and 24 kg/mol, respectively), as well as their derivatives that were modified using periodate oxidation and borohydride reduction. Investigations were carried out in water and dimethyl sulfoxide (DMSO) by means of small angle neutron scattering (SANS). All dispersions of XS and its derivatives were turbid in water and translucent in DMSO. All samples based on XM were translucent in water and transparent in DMSO. In all cases, dispersions showed aggregates at the nanoscale with SANS, even for visually translucent and transparent dispersions with individual chains in a good solvent environment, indicated by the obtained Flory exponent of 0.588. Xylans dispersed in DMSO were less aggregated than xylan dispersed in water. The effect of solvent choice on the dispersibility of the modified xylans depended on the starting material composition. We propose that aggregation on the nanoscale is an intrinsic property of these polysaccharides and must be accounted for in processing, analysis, modification and applications.

We propose that cationic polyelectrolyte molecules deposited on an aqueous solution containing AuCl4 ions can serve as effective templates for the controlled synthesis of gold nanoparticles by the technique of X-ray surface radiolysis. This approach offers the advantage of enabling the in-situ synthesis of metallic nanostructures whose morphologies are determined by the density of the polyelectrolyte layer, and limit the number of chemical byproducts. A diblock copolymer, polystyrene-b-poly(2-(dimethylamino)ethyl methacrylate) (PS-b-PDMAEMA), is spread at the air/aqueous subphase interface using the Langmuir method. The effect of AuCl4-ions on the PS-b-PDMAEMA layer thickness is determined and compared to one obtained on the pure water subphase. Neutron reflectometry revealed that in the presence of AuCl4-ions, a collapse of the PS-b-PDMAEMA chains occurs. The layer thickness is strongly reduced by a factor 4-5 from that of the PS-b-PDMAEMA brush on pure water. The reduction of gold ions is then induced in the vicinity of the interface by X-ray surface radiolysis method. The formation of metallic nanoparticles is monitored in-situ and characterized using grazing incidence X-ray diffraction (GIXD) and total reflection X-ray fluorescence (TRXF). The controlled reduction process by X-rays yielded to the formation of two distinct gold nanostructure morphologies simultaneously: (1) surface-oriented 2D hexagonal nanoplatelets grown directly from the polymer layer, exhibiting crystalline organization confirmed by distinct GIXD patterns with micrometers in plane size and tens of nanometers of thickness as observed by AFM, and (2) spherical nano-colloids of few hundred of nanometers diameters formed in the vicinity of the interface, as demonstrated by GIXD patterns. The work indicates that the approach has potential to form hierarchical material assemblies and has potential for applications in surface-enhanced spectroscopy or heterogeneous catalysis.

We investigated the influence of the partial methyl-esterification of polygalacturonic acid (PGA) chains on the structure of ionotropic hydrogels prepared with an external gelation protocol using calcium as the crosslinker and PGA chains with degrees of methylation (DM) of 0, 3, 18, and 34 %. Molar mass determination, viscosity, and small-angle neutron scattering measurements revealed that the methyl-esterification reaction employed reduces the molar mass (Mw) and the intrinsic viscosity, of the PGA chains and increases their overlap concentration, and their persistence length as DM increases. Moreover, the methylation induces turbidity in Ca-PGA hydrogels, which reflects the emergence of mesoscopic heterogeneities, reduces the gradients in PGA and calcium concentrations, as well as in Young's modulus and increases the mesh size of the hydrogels. Complementary molecular dynamics simulations also showed that methylation promotes 31 helical conformations of PGA chains and reduces the length of junction zones between cross-linked PGA chains in the presence of calcium. Such effects likely originate from the presence of methyl-ester groups, which decreases the negative charge of methylated PGA chains, weakens their affinity for calcium, and promotes irregular association patterns.

HYPOTHESIS:Acoustic levitation is a suitable approach for studying processes occurring at the gas-liquid interfaces, as it allows its investigation in a contact-free manner while providing control over the gas phase. Here, we hypothesize that phase transitions induced by a CO2 rich atmosphere can be examined, at different length scales, in a contact-free manner. EXPERIMENTAL:A system consisting of 12-hydroxysteric acid (HSA) soaps mixed with different ratios of monoethanolamine (MEA) and choline hydroxide, was prepared. Microliter droplets of the samples were acoustically levitated and monitored with a camera, while exposed to CO2 to modify the pH through diffusion at the air-liquid interface and inside the droplet. The phase transition and water mobility in the levitated droplets were evaluated through X-ray scattering (SAXS/WAXS) and magnetic resonance studies, in real-time. Finally, the droplets were collected and examined under the microscope. FINDINGS:The introduction of CO2 gas induced a phase transition from micelles to multi-lamellar tubes, resulting in a gel-like behavior both in the bulk and at the interface. The high stability of the acoustic levitator allowed the investigation of this dynamic phenomenon, in real-time, in a contact-free environment. This study showcases the suitability of acoustic levitation as a tool to investigate complex chemical processes at interfaces.

Photocurable denture bases require both rigidity (high flexural strength and modulus) and high fracture toughness (to prevent cracking or breaking under mechanical stress). These antagonist properties can be provided by the incorporation of block copolymers (BCPs) due to their unique self-assembly properties conferring an overall improvement of fracture toughness and mechanical properties to denture base materials. In the present work, it was shown that poly(methyl methacrylate)-block-poly(dimethyl siloxane)-block-poly(methyl methacrylate) (PMMA-PDMS-PMMA) triblock copolymers are highly efficient toughening agents for (meth)acrylic resins, resulting in a significantly improved fracture toughness without compromising the mechanical strength or processing. The influence of the PMMA:PDMS block ratio and the weight fraction of triblock copolymer (3-10 wt %) in the resin was investigated and revealed that the most efficient toughening triblock copolymer is composed of PMMA and PDMS blocks having the similar molecular weight of 8000 g mol-1. The highest fracture toughness value (Kmax = 2,25 MPa m1/2) was obtained with this BCP at a concentration of 5 wt% in the resin, an improvement of 180 % compared to the BCP free resin. Small angle X-ray scattering measurements revealed that self-assembly of BCPs led to the formation of spherical micelles that transform to small clusters after curing if the compatible PMMA block is sufficiently long compared to the incompatible PDMS block. Otherwise, large aggregates were observed. Transmission electron microscopy confirmed the SAXS results, showing the clusters of spherical micelles. As toughening agents, PMMA-PDMS-PMMA BCPs showed better performance than the reference polycaprolactone-polysiloxane (PCL-PDMS-PCL) one. The influence of the nature of the compatible block (PMMA versus PCL) and of the PMMA:PDMS block ratio on the fracture toughness of radical-cured resin systems was clearly demonstrated in this study. The most promising formulation was shown to be suitable for digital light processing 3D printing.

The effect of periodate oxidation and borohydride reduction on arabinoxylan (AX) in aqueous solution was investigated using 13C NMR spectroscopy and small-angle X-ray scattering (SAXS). AX consists of a xylose backbone, which is mono- or di-substituted with arabinose. We show that at a ring-opening modification degree of 21%, periodate oxidation occurs predominantly on arabinose, and shows a preference for arabinose linked to di-substituted xylose units over the mono-substituted. With a higher degree of modification of 33%, arabinose at the mono-substituted position and unsubstituted xylose units are also modified. At 33% a large portion of oxidizable AX residues have been ring-opened, yet SAXS reveals no significant changes in chain conformation and only a minor reduction (10%) in persistence length for the oxidized-reduced dialcohol AX. With increasing degree of oxidation, dialdehyde AX instead show an increasing tendency for aggregation, attributed to chain cross-linking. Upon reduction of the dialdehyde and cross-linked groups to dialcohol AX, the chains revert back to having repulsive interactions, acting as chains in a good solvent environment.

HYPOTHESIS:The mixing of end-capped poly(ethylene glycol) (PEG) chains with 12-hydroxy stearic acid (12-HSA) molecules is a simple one-pot strategy to design thermo-responsive PEGylated self-assemblies of fatty acids with various morphology types at room temperature (multi-lamellar tubes or vesicles) that transit reversibly upon heating into small micelles around physiological temperature. EXPERIMENTAL:4 types of 4k end-capped poly(ethylene glycol) (PEG) chains, capped respectively at one end or at both ends with either 12-HSA or stearic acid (SA), were mixed with 12-hydroxy stearic acid molecules, at a low constant ratio of end capped fatty acid moieties brought by the chains to that of free 12-HSA molecules. The detailed structure of the self-assemblies of mixtures was obtained using Small Angle Neutron Scattering with contrast variation at both 20 °C and 45 °C, and their temperature-dependent rheological behavior was characterized. FINDINGS:For both types of mono-functionalized PEG, the chains insert homogenously in the multi-lamellar tubes formed by 12-HSA molecules. The mixtures of di-functionalized chains by 12-HSA with 12-HSA molecules produce PEGylated vesicles, since the change of packing parameter induced by insertion of the telechelic chains no longer allows the formation of tubes. Conversely, mixtures of di-functionalized chains by SA with 12-HSA molecules enable to keep multi-lamellar tubes, a specific behavior that likely comes from the fact that they only insert by one end within the 12-HSA bilayers. All systems transit reversibly into small PEGylated ellipsoidal micelles. The morphological transitions enable to tune the rheological properties of suspensions, that are gelled at low temperature and turn Newtonian liquid at around 37 °C.

Some of the most promising fields of application of ionic liquid-based colloids imply elevated temperatures. Their careful design and analysis is therefore essential. The system studied are iron oxide nanoparticles (NPs) dispersed in ethyl-methylimidazolium bistriflimide (EMIM TFSI). The key parameters of the solid-liquid interface, tuned at room temperature, are the surface charge density and the nature of the counterions. The thermal stability of these nanoparticle dispersions is then analysed on the short and long term up to 473 K. A multiscale analysis is performed combining dynamic light scattering (DLS), small angle X-ray/neutron scattering (SAXS/SANS) and thermogravimetric analysis (TGA). With a careful choice of the species at the solid-liquid interface, ionic liquid-based colloidal dispersions of iron oxide NPs in EMIM TFSI stable over years at room temperature can be obtained, also stable at least over days up to 473 K and NPs concentrations up to 12 vol% (30 wt%).

Arabinoxylan (AX) with varying arabinose to xylose (A/X) ratios of 0.85, 0.57 and 0.39 was extracted from wheat bran, and the conformations of the AX polysaccharides dispersed in water were investigated using small-angle X-ray scattering. The persistence length (Lp) and the conformation statistics (expressed by the Flory exponent v or the mass fractal) of the AX varied with their A/X ratios. The Lp decreased with decreasing A/X ratio, from 4.5 nm to 1.5 nm, where the AX with high and intermediate A/X ratios can be considered semi-flexible chains, while AX with the lowest A/X ratio behaves as a flexible chain. The mass fractal increased from 1.7 to 2.5 between the highest and lowest A/X ratios, indicating increasingly compact polymer conformations. AX with the highest A/X ratio behaved as chains in a good solvent and was well dispersed even in the semi-dilute regime. AX with intermediate and low A/X ratios showed stronger tendencies to aggregate and were not well dispersed at higher concentrations. The results presented show that the macroscopic properties of AX dispersions can be understood based on the chemical composition and fine structure of the AX polysaccharide.

We report a novel class of nanocomposite physical hydrogels based on polyacrylamide networks, where the crosslinking is achieved through complex nanostructures.

An scalable method for the fabrication of symmetric and asymmetric BC bilayers on solid support of any type, shape and size is proposed, in order to overcome the specific limitations of currently available techniques (notably Langmuir-Blodgett (LB) deposition and polymersome vesicle fusion (VF)). We demonstrated that this fabrication process is viable by developing a proof of concept on silicon wafers, flat and macro-scopic substrates that allow the use of a wide range of complementary state-of-the-art techniques to precisely characterize the different steps of the assembly. This type of assembly, however, is potentially possible on colloidal objects, as showed by preliminary results. The proposed fabri-cation method was done using polystyrene-block-poly(acrylic acid) block copolymer and consists of two steps: i) the formation of a monolayer of BCs by the establishment of non-covalent interactions between the substrate and the hydrophilic blocks in a non-selective solvent ii) the controlled addition of a selective solvent (water) which triggers the assembly of the second layer through hydrophobic interactions between the free and previously adsorbed hydrophobic blocks resulting in the formation of a self-assembled bilayer of BCs on a solid support. A final rinsing step allows to eliminate the excess of aggregates (micelles) generated in the solution during the second step. BC monolayers and bilayers on solid supports were obtained and characterized using various surface characterization techniques. The ability of these bilayers to encapsulate hydrophobic actives of interest for specific applications has also been highlighted using gold nanoparticles (AuNPs). Finally, the possibility to form asymmetric bilayers was demonstrated on a PS-b-PAA/PS-b -poly(vinyl pyridine) (PS-b-P2VP) system.

Nanoparticles (NPs) of iron oxide are dispersed in mixtures of water and ionic liquid, here ethylammonium nitrate (EAN), and the NP/NP and NP/solvent interactions are studied. They are analysed via small-angle X-ray scattering and dynamic light scattering coupled to forced Rayleigh scattering, from 22 degrees C to 80 degrees C. The NPs are well-dispersed as individual objects in the whole range of compositions and temperatures thanks to sufficient repulsion due to the organization of the solvents at the interface. The surface changes from hydrophilic to hydrophobic around a proportion of 50 vol% water : 50 vol% EAN, following the evolution of the bulk mixtures, which remain heterogeneous in the whole range of compositions. Nanoparticles of iron oxide are dispersed in mixtures of water and ionic liquid, here ethylammonium nitrate, and the NP/NP and NP/solvent interactions are studied.

HypothesisOrganohydrogel emulsions display unique rheological properties and contain hydrophilic and lipophilic domains highly desirable for the loading of active compounds. They find utility in various applications from food to pharmaceuticals and cosmetic products. The current systems have limited applications due to complex expensive formulation and/or processing difficulties in scale-up. To solve these issues, a simple emulsification process coupled with unique compounds are required.ExperimentsHere, we report an organohydrogel emulsion based only on a low concentration of 12-hydroxystearic acid acting as a gelling agent for both oil and water phases but also as a surfactant. The emulsification process is based on in-situ surfactant transfer. We characterize the emulsification process occurring at the nanoscale by using tensiometry experiments. The emulsion structure was determined by coupling Small Angle X-ray and neutron scattering, and confocal Raman microscopy.FindingsWe demonstrate that the stability and unique rheological properties of these emulsions come from the presence of self-assembled crystalline structures of 12-hydroxystearic acid in both liquid phases. The emulsion properties can be tuned by varying the emulsion composition over a wide range. These gelled emulsions are prepared using a low energy method offering easy scale-up at an industrial level.

To further our understanding of a thermoplastic arabinoxylan (AX) material obtained through an oxidation-reduction-etherification pathway, the role of the initial arabinose:xylose ratio on the material properties was investigated. Compression molded films with one molar substitution of butyl glycidyl ether (BGE) showed markedly different tensile behaviors. Films made from low arabinose AX were less ductile, while those made from high arabinose AX exhibited elastomer-like behaviors. X-ray scattering confirmed the presence of nanostructure formation resulting in nano-domains rich in either AX or BGE, from side chain grafting. The scattering data showed variations in the presence of ordered structures, nano-domain sizes and their temperature response between AX with different arabinose contents. In dynamic mechanical testing, three transitions were observed at approximately -90 °C, -50 °C and 80 °C, with a correlation between samples with more structured nano-domains and those with higher onset transition temperatures and lower storage modulus decrease. The mechanical properties of the final thermoplastic AX material can therefore be tuned by controlling the composition of the starting material.

Despite the high impact lithium-sulfur (Li-S) batteries can bring in terms of specific energy and battery lifetime, their full advantage has not yet been realized due to inherent issues associated with this technology. The intermediate polysulfide products produced in the positive electrode during discharge dissolve and diffuse in the electrolyte, leading to capacity fading and low Coulombic efficiency. A promising solution to this issue is the use of a solid polymer electrolyte that combines the advantages of an ion-conducting poly(ethylene oxide) (PEO) phase and a mechanically reinforced phase, such as polystyrene (PS), that can suppress the nonuniform electrodeposition of Li onto Li metal. In this work, the possibility of using PS-PEO-PS triblock copolymer as an electrolyte or binder in a Li-S battery was investigated by characterizing the thermodynamical, morphological, and ionic transport properties of lithium polysulfides species (Li2S x , with x = 4 and 8). Thermodynamic results showed that the long-chain lithium polysulfide (Li2S8) is more soluble in the copolymers compared to the short-chain polysulfide (Li2S4). Meanwhile, the addition of Li2S4 and Li2S8 in the mesostructured block copolymer influences both the phase transition (lamellar or hexagonal) and the domain spacing in a fashion similar to the conventional LiTFSI salt. In terms of ionic transport, the mobility of the polysulfides (S4 2- and S8 2-) in the copolymers is reduced compared to the TFSI- anion, and the cationic transference number remains in the range of 0.5 compared to 0.15 for LiTFSI. To move toward the application, the introduction of Li2S4 into the block copolymer electrolyte is also used as an additive in the presence of LiTFSI salt, resulting in a very low interfacial resistance with the Li metal electrode. The results of these investigations would guide the design of solid polymer electrolytes for application in Li-S batteries.

We describe the aqueous behavior of short Polyethylene glycol (PEG) chains of Mw 4 kDa that are either mono-functionalized or di-functionalized by 12-hydroxy stearic acid (HSA), and stearic acid (SA), respectively. The end capping of the chains by the fatty acids is achieved by Steglich esterification, after a step of protection of the 12-OH functional group in the case of HSA. Small Angle Neutron Scattering (SANS) shows that mono-functionalized chains with both SA or HSA sticky ends self-assemble in star micelles in aqueous solution, and interact through repulsive steric interactions. The di-functionalized telechelic chains self-assemble in flower micelles that interact through interactions that are attractive on average due to the formation of bridges by chains that share their both ends in two different micelles. Solutions of telechelic chains undergo a phase separation between a dilute solution of micelles and a dense hexagonal crystalline network of flower micelles above a given polymer concentration threshold. This threshold is lower for SA-PEG-SA than for HSA-PEG-HSA. We postulate that this difference of behavior arises from the formation of hydrogen bonds between the OH groups at the C12 of the alkyl chain in case of HSA that increase the stability of the hydrophobic core of the micelles.