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Responsive liquid marbles (LMs), which can change their shape, stability, and motion by the application of stimuli, attract a growing interest due to their wide range of applications. Our approach to design photo- and thermoresponsive LMs is based on the use of micrometer-sized fatty acid (FA) particles as phase change material covered with polypyrrole (PPy) overlayers with photothermal property. The core-shell particles were synthesized by aqueous chemical oxidative seeded dispersion polymerization. First, we investigated the effect of the alkyl chain length of FA on the resulting FA/PPy core-shell particles by characterizing their size and its distribution, shape, morphology, chemical composition, and photothermal behavior. Then LMs were fabricated by rolling water droplets on the dried FA/PPy particle powder bed and their light and temperature dual stimuli-responsive nature was studied as a function of the FA alkyl chain length. For all FAs studied, LMs disrupted in a domino manner by light irradiation as the first trigger: the temperature of the FA/PPy particles on the LM surface increased by light irradiation, followed by phase change of FA core of the particles from solid to liquid, resulting in disruption of the LM and release of the encapsulated water. The disruption time was closely correlated to the melting point of FA linked to the alkyl chain length and light irradiation power, and it could be controlled and tuned easily between quasi instantaneous and approximately 10 s. Finally, we showed potential applications of the LMs as a carrier for controlled delivery and release of substances and a sensor.

Surfactant crystals can stabilize liquid foams. The crystals are adsorbed at bubble surfaces, slowing down coarsening and coalescence. Excess crystals in the liquid channels between bubbles arrest drainage, leading to ultrastable foams. The melting of crystals upon raising the temperature allows thermoresponsive foams to be designed. In the case of oil foams, the stabilization by crystals received substantial renewed interest in the last 5 years due to their potential applications, particularly in the food industry. For aqueous foams, several reports exist on foams stabilized by crystals. However, these two kinds of liquid foams possess similarities in terms of stabilization mechanisms and the design of surfactant crystal systems. This field will certainly grow in the coming years, and it will contribute to the engineering of new soft materials not only for food but also for cosmetics, pharmaceuticals, and biomedical applications.

International audience; Fatty acids are widely used in industries for various applications as soaps or in their crystalline form. Fatty acid soaps are used as surface-active agent to stabilize foams and emulsions, for detergency, and surface wetting. Fatty acid molecules in organic solvents are used as low-molecular-mass organic gelators. Currently, there is a renewed interest in using fatty acids in industrial applications instead of petrochemical surfactants since fatty acid soaps are green surfactants. Fatty acids exhibit also many advantages, including the design of responsive soft-materials. Fatty acid soaps are natural pH and thermoresponsive surfactants, which can lead to responsive foams and emulsions. In their crystalline form, fatty acid crystals in both aqueous and non-aqueous solvents stabilize liquid foams. These crystals are also efficient in the production of liquid marbles. Fatty acids are solvosurfactants with the ability to form microemulsions and capillary suspensions. In this review, we illustrate how fatty acid molecules can be used in the manufacture of multiresponsive soft-materials ranging from aqueous and non-aqueous foams, emulsions, nanoemulsions, microemulsions, liquid marbles and capillary suspensions.

The crucial roles of the ionization state and counterion presence on the phase behavior of fatty acid in aqueous solutions are well-established. However, the effects of counterions on the adsorption and morphological state of fatty acid on nanoparticle surfaces are largely unknown. This knowledge gap exists due to the high complexity of the interactions between nanoparticles, counterions, and fatty acid molecules in aqueous solution. In this study, we use adsorption isotherms, small angle neutron scattering, and all-atom molecular dynamic simulations to investigate the effect of addition of ethanolamine as a counterion on the adsorption and self-assembly of decanoic acid onto aminopropyl-modified silica nanoparticles. We show that the morphology of the fatty acid assemblies on silica nanoparticles changes from discrete surface patches to a continuous bilayer by increasing concentration of the counterion. This morphological behavior of fatty acid on the oppositely charged nanoparticle surface alters the interfacial activity of the fatty acid–nanoparticle complex and thus governs the stability of the foam formed by the mixture. Our study provides new insights into the structure–property relationship of fatty acid–nanoparticle complexes and outlines a framework to program the stability of foams formed by mixtures of nanoparticles and amphiphiles.

Recently, we described that the weight ratio (

International audience; Aqueous foams are encountered in many commercial products used in our everyday lives and are widely studied. However, the formation and stabilization of foams using high alcohol content (>75%) solvents such as ethanol is still a scientific challenge. Herein, we report for the first-time foams based on high ethanol content showing long-term stability by using natural fatty acid crystals. The platelet-shape crystals are adsorbed at the air-water surface protecting the bubbles against coalescence. The melting of crystals triggers the foam destabilization leading to thermostimulable high ethanol content foams. These foams can be used as a new formulation strategy for alcohol-based hand sanitizers to better clean hands, protect the skin by the presence of fatty acids, and limit the transmission of virus and other pathogens. (c) 2021 Elsevier Inc. All rights reserved.

Hypothesis In oleogel food systems (based on the mixture between stearic acid and stearyl alcohol) the strong effect of the weight ratio (R) between these two components on the textural and structural properties is well described. The effect of R for other fatty acids and fatty alcohols is less explored. Moreover, they do not show an enhancement of the oleogel properties for specific R. The effect of R on the oleogel properties, for a mixture of fatty acid and fatty alcohol with longer alkyl chains (behenyl alcohol and behenic acid) in sunflower and soybean oils, which are raw materials widely used in cosmetic and pharmaceutical industries, was investigated. Experiments We characterized the oleogel properties as a function of R in terms of structuring potential: hardness, oil loss and gel stability. This information was correlated with microstructural data obtained at different length scales by coupling optical microscopy, DSC, SFC, SAXS and WAXS experiments. Findings Our results highlight that R tunes the oleogel properties in a comparable manner to previous results obtained for stearic acid and stearyl alcohol-based oleogels. Two specific R (8:2 and 7:3) close to the 3:1 molecular ratio gave oleogels with both the highest hardness and stability. The morphology and size of the mixed crystals obtained for these R cannot solely explain why they are stronger gels with low oil loss in comparison to the other R. The almost complete crystallization for these two R is one of the key parameters controlling the oleogel properties. As described in the literature, we also suggest that the differences in oleogel properties come from the spatial distribution of the crystalline mass. In this study, we confirm that the effect of the 3:1 molecular ratio in mixed surfactant systems described more than 50 years ago for foams, emulsions and Langmuir monolayers occurs also on the crystallization of mixed fatty alcohol and fatty acid in oils leading to better oleogels properties.

Oil foams could be used to create food products with reduced fat content in combination with new textures. The incorporation of air bubbles in an oily continuous phase could provide a different mouthfeel and appearance to oil products. Moreover, they could enhance flavour delivery by the inclusion of air containing odorant compounds. This chapter aims to describe how to produce edible oil foams from vegetable oils based on Ramsden-Pickering stabilization by crystal particles. When emulsions are stabilized by particles, they are commonly called Ramsden emulsions or Pickering emulsions, after the pioneering researchers in this field. Following this trend for emulsions, foams stabilized by particles are referred to as Pickering foams. To obtain edible crystalline particles, commercial mono/diglyceride surfactants, long-chain alcohols, long-chain carboxylic acids, triglycerides, sucrose esters and sunflower lecithin can be used. The presence of the crystalline particles both at the interface and in the continuous phase stabilizes the oil foam.

International audience; We have investigated the ability to monitor the dynamics transition phase of various substances by resonant probe light. Such a specific Micro-Total Analysis Systems (µTAS) can be used in food, cosmetic and biology applications. Such lab-on-chip sensors present the possibility of data treatment with an embedded system. The serial of transduced spectra are then acquired with an optical spectrum analyzer linked to a computer on which Matlab software record and process the data in real time. Then specific quantities can be linked to the intrinsic physico-chemical characteristics of the substances. As an example (not exhaustive) the development and the ability of an optical integrated polymeric resonator, acting as a surface light probe, for monitoring temperature-induced supramolecular phase transitions will be presented. The homogeneous detection of the transitions between different self-assembled structures in an aqueous solution of fatty acids (12-hydroxystearic acid, in association with amino-pentanol) was studied by investigating the coupling between the solution and the integrated photonic micro-cavity. Tuning the self-organized assemblies of surfactant is very attractive for many applications, such as cosmetic products, food, drug delivery and medical, and the development of alternative tools-especially those requiring minute amount of solution-to monitor their structural changes are essential. These original studies at temperatures ranging from 17 to 24 °C, based on a statistical treatment of optical resonance spectra, have evidenced the thermoresponsive nature of the optical features, and that different regimes occur with temperature. The optical results were corroborated with the measurement of the solution viscosity as a function of temperature, confirming that we can ascribe the optically-detected regimes to a surfactant assembly shifting reversibly from a tubular shape to a micellar one. The comparison between the optical and the rheological responses showed different accuracies: while the viscosity data exhibited a rather smooth and monotonous transition, the behavior changes were sharper and non-monotonous in terms of optical properties, allowing us to unambiguously identify in intermediate regime between 18.5 and 20°C. These morphological transition experiments represent a unique opportunity to extend the numbers of available techniques studying these systems through integrated optical techniques with potential opportunities of real time detection and working on low sampling volume. Other examples will be developed as the detecting of phase transition of sphingomyelin in biology and health corroborate by differential scanning calorimetry…

Oil foams that are based on oleogels are stabilized by the presence of crystalline particles at the air bubble surface and in bulk. The size of crystalline particles is an important parameter in oil foam stabilization. The creation process (cooling and shear rate) can tune its properties. The aim of this study was to determine the effect of altering the weight ratio (R) between long chain fatty acids and fatty alcohols on the oil foam. Two optimal weight ratios R = 7:3 and R = 8:2, for which mixed crystals were present, produced the best foams in terms of overrun, foam firmness and foam stability. R not only affected the crystal size, but also the number of crystalline particles present in the oleogel. Mixed crystals help to produce and stabilize the foams. We highlighted that there is a link between the oleogel stability and hardness with their resulting oleofoam properties.

International audience; The development and the ability of an optical integrated polymeric resonator, acting as a surface light probe, for monitoring temperature-induced supramolecular phase transitions is presented in this work. The homogeneous detection of the transitions between different self-assembled structures in an aqueous solution of fatty acids (12-hydroxystearic acid, in association with amino-pentanol) was studied by investigating thecoupling between the solution and the integrated photonic micro-cavity. Tuning the self-organized assemblies of surfactant is very attractive for many applications, such as cosmetic products, food, drug delivery and medical, and the development of alternative tools – especially those requiring minute amount of solution – to monitor their structural changes are essential. These original studies at temperatures ranging from 17 to 24 ◦C, based on a statistical treatment of optical resonance spectra, have evidenced the thermoresponsive nature of the optical features, and that different regimes occur with temperature. The optical results were corroborated with the measurement of the solution viscosity as a function of temperature, confirming that we can ascribe the optically-detected regimes to a surfactant assembly shifting reversibly from a tubular shape to a micellar one. The comparison between the optical and the rheological responses showed different accuracies: while the viscosity data exhibited a rather smooth and monotonous transition, the behavior changes were sharper and non-monotonous in terms of optical properties, allowing us to unambiguously identify in intermediate regime between 18.5 and 20 ◦C. These morphological transition experiments represent a unique opportunityto extend the numbers of available techniques studying these systems through integrated optical techniques with potential opportunities of real time detection and working on low sampling volume.

International audience; Themost common types of liquid foams are aqueous ones, and correspond to gas bubbles dispersed in an aqueousliquid phase. Non-aqueous foams are also composed of gas bubbles, but dispersed in a non-aqueous solvent. In theliterature, articles on such non-aqueous foams are scarce; however, the study of these foams has recently emerged,especially because of their potential use as low calories food products and of their increasing importance in variousother industries (such as, for instance, the petroleum industry).Non-aqueous foams can be based on three differentfoam stabilizers categories: specialty surfactants, solid particles and crystalline particles. In this review, we onlyfocus on recent advances explaining how solid and crystalline particles can lead to the formation of non-aqueousfoams, and stabilize them. In fact, as discussed here, the foaming is both driven by the physical properties of theliquid phase and by the interactions between the foam stabilizer and this liquid phase. Therefore, for a given stabilizer,different foaming and stability behavior can be found when the solvent is varied. This is different fromaqueoussystems forwhich the foaming properties are only set by the foam stabilizer.We also highlight how these nonaqueousfoams systems can easily become responsive to temperature changes or by the application of light.

A comprehensive review of the features driving self-assembly of 12-hydroxystearic acid (12-HSA), a low-molecular-weight gelator, and its applications in drug delivery and as other soft innovative materials are presented herein. 12-HSA is obtained via hydrogenation of ricinoleic acid naturally found in high concentrations in castor oil. The ability of 12-HSA to self-assemble is associated with the presence, position, and enantiomeric purity of the hydroxy group along the fatty acid chain. The polarity and position of the hydroxyl group facilitates more interaction possibilities leading to its exceptional self-assembly behavior giving rise to fibers, ribbons, and tubes in a variety of solvents. Upon self-assembly, 12-HSA undergoes crystallization resulting in the formation of high aspect ratio fibrillar structures due to noncovalent, intermolecular interactions forming self-spanning, three-dimensional networks (called self-assembled fibrillar networks) in both aqueous and organic solvents. Herein, emphasis is placed on emerging applications of 12-HSA supramolecular assemblies (i.e. responsive aqueous foams, gelled complex fluids, drug delivery systems, hydrogels, organogels, xerogels, and aerogel). The vast literature is compiled associated with 12-HSA self-assembly exploring supramolecular assemblies based on one ambidextrous gelator capable of assembling in aqueous and nonaqueous solvent.

The development of shampoo and cleansing formulations in cosmetics is at a crossroads due to consumer demands for better performing, more natural products and also the strong commitment of cosmetic companies to improve the sustainability of cosmetic products. In order to go beyond traditional formulations, it is of great importance to clearly establish the science behind cleansing technologies and appreciate the specificity of cleansing biological surfaces such as hair and skin. In this review, we present recent advances in our knowledge of the physicochemical properties of the hair surface from both an experimental and a theoretical point of view. We discuss the opportunities and challenges that newer, sustainable formulations bring compared to petroleum-based ingredients. The inevitable evolution towards more bio-based, eco-friendly ingredients and sustainable formulations requires a complete rethink of many well-known physicochemical principles. The pivotal role of digital sciences and modelling in the understanding and conception of new ingredients and formulations is discussed. We describe recent numerical approaches that take into account the specificities of the hair surface in terms of structuration, different methods that study the adsorption of formulation ingredients and finally the success of new data-driven approaches. We conclude with practical examples on current formulation efforts incorporating bio-surfactants, controlling foaming and searching for new rheological properties.

Stimuli-responsive liquid foams and bubbles are systems for which the stability, structure, shape, and movement can be controlled by the application of stimuli. The foam stability can be modified by a stimulus which can change solution condition (pH, temperature, and ionic strength) or with the application of an external field (light and magnetic). Different foam stabilizers have been described in the literature to design these responsive foams systems ranging from surfactants, peptides, polymers, soft polymer particles, surfactants self-assembly, crystalline particles, emulsion droplets, and solid particles. This review aims to cover the recent advances of the design of stimuli-responsive liquid foams and their applications. Responsive liquid foams are attractive in textile coloring process, biomedical application, washing, and material recovery processes.

The interfacial and foam properties of a model system based on the mixture between myristic acid and choline hydroxide have been investigated as a function of the molar ratio (R) between these two components and temperature. The aim of this study was to obtain insight on the links between the self-assemblies in bulk and in the foam liquid channels, the surfactant packing at the interface, and the resulting foam properties and stability. A multiscale approach was used combining small angle neutron scattering, specular neutron reflectivity, surface tension measurements, and photography. We highlighted three regimes of foam stability in this system by modifying R: high foam stability for R < 1, intermediate at R ∼ 1, and low for R > 1. The different regimes come from the pH variations in bulk linked to R. The pH plays a crucial role at the molecular scale by setting the ionization state of the myristic acid molecules adsorbed at the gas-liquid interface, which in turn controls both the properties of the monolayer and the stability of the films separating the bubbles. The main requirement to obtain stable foams is to set the pH close to the pKa in order to have a mixture of protonated and ionized molecules giving rise to intermolecular hydrogen bonds. As a result, a dense monolayer is formed at the interface with a low surface tension. R also modifies the structure of self-assembly in bulk and therefore within the foam, but such a morphological change has only a minor effect on the foam stability. This study confirms that foam stability in surfactant systems having a carboxylic acid as polar headgroup is mainly linked to the ionization state of the molecules at the interface. Fil: Arnould, Audrey. No especifíca; Fil: Cousin, Fabrice. No especifíca; Fil: Salonen, Anniina. No especifíca; Fil: Saint Jalmes, Arnaud. Centre National de la Recherche Scientifique; Francia Fil: Perez, Adrián Alejandro. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Fameau, Anne Laure. No especifíca

International audience; Thermoresponsive foams that refer to foams for which the stability can be switched between the stable and unstable state have recently attracted growing interest due to their possible industrial applications. Our approach to design such foams is based on the use of fatty acids, with various counterions and molar ratios. It is the first example of foams with a temperature threshold of destabilization which can be continuously set between 20 °C and 75 °C.

International audience; Hypothesis: In fatty acid systems, the role of the nature of the counter-ion on their solubility is well described. However, the effect of the molar ratio (R) between the fatty acid and its counter-ion is less explored. We investigated the effect of R as a function of the temperature in aqueous solution between myristic acid and two organic amines under hydroxide form: tetramethylammonium (TMAOH) and benzyltrimethylammonium hydroxide (BTAOH). We compare with the results previously obtained for choline hydroxide as counter-ion (Arnould et al., 2015). Experiments: We characterized the phase behavior by coupling phase-contrast microscopy, SANS, DSC and WAXS experiments. The myristic acid ionization state was determined by pH, conductivity and infra-red spectroscopy measurements. Findings: Our results highlight that R tunes the phase behavior. The amount of hydroxide groups in solution fixes the ionization state of the fatty acids, which governs the headgroup interactions. At low R, the counter-ion hydrophobicity plays a role on the phase behavior: TMAOH and choline hydroxide shows a broad polymorphism (facetted and unilamellar vesicles, lamellar phases) due to their hydrophilicity while the more hydrophobic BTAOH gives fatty acid crystals at low temperatures and vesicles at high temperatures. At high R, spherical micelles are observed for all counter-ions.

The most common types of foams are aqueous foams. Non-aqueous foams are composed of gas bubbles dispersed in a non-aqueous phase. The physical properties of the non-aqueous liquid phase drive the foaming properties. Contrary to aqueous foams, the foaming properties are not only related to the foaming capacity of the foam stabilizer, but are linked to the nature of the non-aqueous phase and to the interactions between this liquid phase and the foam stabilizer. In the literature, non-aqueous foams are scarcely studied. However, this topic is important for various industries, such as the petroleum industry. New interest in these systems has emerged recently owing to their potential use in low-calorie food products. The non-aqueous foams can be produced based on three different foam stabilizer categories: surfactants, solid particles and crystalline particles. The crystalline particles are also well known in the literature to be involved in the formation of oleogels. Therefore, edible oil foams can be obtained based on oleogels. In this book chapter, the more recent advances in the non-aqueous foams field are described. The mechanisms leading to the formation and stabilization of these non-aqueous foams are described with a focus on oil foams based on oleogel systems.

International audience; In surfactant systems, the major role of the nature of the counter-ion on the surfactant behavior is well-known. However, the effect of the molar ratio between the surfactant and its counter-ion is less explored in the literature. We investigated the effect of the molar ratio (R) between 12-hydroxystearic acid (12-HSA) and various alkanolamines as a function of the temperature in aqueous solution from the molecular scale to the mesoscale. By coupling microscopy techniques and small angle neutron scattering, we showed that 12-HSA self-assembled into multilamellar tubes and transitioned into micelles at a precise temperature. This temperature transition depended on both the molar ratio and the alkyl chain length of the counter-ion and could be precisely tuned from 20°C to 75°C. This thermal behaviour was investigated by differential scanning calorimetry and wide angle X-ray scattering. We highlighted that the transition at the supramolecular scale between tubes to micelles came from two different mechanisms at the molecular scale as a function of the molar ratio. At low R, with an excess of counter-ion, the transition came from the chain melting phenomenon. At high R, with an excess of 12-HSA, the transition came from both the chain melting process and the surface melting process of the hydrogen bonds. At the mesoscale, this transition of supramolecular assemblies from tubes to micelles, delimited a regime of high bulk viscosity, with a regime of low viscosity.

Surfactants, which are molecules bearing a hydrophobic part and a hydrophilic part, are widely used in many daily life products (detergent, cosmetic, pharmaceutical...) because of their foaming properties. Indeed, they spontaneously go to the interface between air and water, which stabilizes the thin water films surrounding air bubbles to obtain foams. Currently, since the most used surfactants come from derivatives from petroleum-based products, their replacement by biomolecules is a major issue in the current context of sustainable development and green chemistry. This could promote the use of molecules from agricultural resources, such as hydroxyl fatty acids that can be extracted from oil or from the tegument of fruits and vegetables, as new agro-based surfactants. Here, we present recent research on the surfactant properties of the 12-hydroxy stearic acid coming from the castor oil. This fatty acid has very advantageous foaming properties compared to conventional synthetic surfactant systems: it enables the production of foams which are at the same time very abundant and, remarkably, stables over a span lasting more than 6 months. Moreover, these foams are thermoresponsive because the foam stability can be easily modulated by a simple modification of the temperature.

COST [MP 1106]; INRA; Region Pays de la Loire; U.S. Army Research Office [W911NF-15-1-0115]; NSF Research Triangle MRSEC on Programmable Soft Matter [DMR-1121107]; International audience; Oil foams are composed of gas bubbles dispersedin an oil phase. These systems are scarcely studied despite theirgreat potential in diverse fields such as the food and cosmeticindustries. Contrary to aqueous foams, the production of oilfoams is difficult to achieve due to the inefficiency of surfactantadsorption at oil−air interfaces. Herein, we report a simple way toproduce oil foams from oleogels, whose liquid phase is a mixtureof sunflower oil and fatty alcohols. The temperature at which theoleogel formed was found to depend on both fatty alcohol chainlength and concentration. The air bubbles in the oleogel foamwere stabilized by fatty alcohol crystals. Below the meltingtemperature of the crystals, oleogel foams were stable for months.Upon heating, these ultrastable foams collapsed within a few minutes due to the melting of the crystal particles. The transitionbetween crystal formation and melting was reversible, leading to thermoresponsive nonaqueous foams. The reversible switchingbetween ultrastable and unstable foam depended solely on the temperature of the system. We demonstrate that these oleogelfoams can be made to be photoresponsive by using internal heat sources such as carbon black particles, which can absorb UVlight and dissipate the absorbed energy as heat. This simple approach for the formulation of responsive oil foams could be easilyextended to other oleogel systems and could find a broad range of applications due to the availability of the components in largequantities and at low cost.

International audience; Fatty acids are natural, pH-responsive surfactants. Their properties can be tuned by adding CO2 or by applying light which modify solution pH. We investigated photoresponsive systems based on fatty acids with different chain lengths in the presence of a photoacid generator (PAG). Under UV irradiation, photolysis of the PAG in aqueous solution resulted in a decrease in pH, triggering a change in fatty acid assembly. Using a multi-scale approach before and after UV irradiation, we characterized the effect of this pH decrease on the nature of the fatty acid self-assemblies. At the molecular scale, pH and infrared spectroscopy measurements were used to determine the fatty acid ionization state. At the microscopic scale, the self-assembled structure was characterized using small-angle neutron scattering and microscopy. We showed that UV irradiation tuned the ionization state of the fatty acid molecules which in turn triggered a transition from spherical micelles to vesicles or lamellar phases, depending on fatty acid chain length. We studied the foaming properties of these systems before and after UV irradiation. We showed that after uv irradiation, foam stability was drastically enhanced as a result of a change in self-assembly. Our approach can be easily extended to various pH-responsive surfactants.

Salt-free catanionic systems based on fatty acids and cationic surfactants are known to exhibit a broad polymorphism by simply tuning the molar ratio between the two components. In the case of fatty acid combined with organic amino counter-ions, very few data are available on the phase behavior obtained as a function of the molar ratio between the counter-ion and the fatty acid. In this study, we investigated the choline hydroxide/myristic acid system as a function of the molar ratio, R= n choline hydroxide/n myristic acid, and the temperature. At molecular scale, the ionization state of myristic acid was determined as a function of R by coupling pH, conductivity and infra-red spectroscopy measurements. At microscopic scale, the self-assemblies were characterized by small angle neutron scattering and microscopy experiments.For R1, all the myristic acid molecules were under their ionized form and only spherical micelles were present in solution. As in the case of catanionic systems, our study highlights that both R and temperature are two key parameters to finely control the self-assembly structure formed by myristic acid in the presence of choline hydroxide. Fil: Arnould, Audrey. Institut National de la Recherche Agronomique; Francia Fil: Perez, Adrián Alejandro. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología de los Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; Argentina Fil: Gaillard, Cédric. Institut National de la Recherche Agronomique; Francia Fil: Douliez, Jean Paul. Institut National de la Recherche Agronomique; Francia Fil: Cousin, Fabrice. Centre National de la Recherche Scientifique; Francia Fil: Santiago, Liliana Gabriela. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Instituto de Tecnología de los Alimentos; Argentina Fil: Zemb, Thomas. Centre National de la Recherche Scientifique; Francia Fil: Anton, Marc. Institut National de la Recherche Agronomique; Francia Fil: Fameau, Anne Laure. Institut National de la Recherche Agronomique; Francia

NSF Research Triangle MRSEC on Programmable Soft Matter DMR-1121107; International audience; The directed assembly of colloidal particles into linear chains and clusters is of fundamental and practical importance. In this study we characterize and analyse the mechanism of the magnetic field driven assembly of lipid-coated iron oxide nanoparticles into flexible microfilaments. Recently we showed that nanocapillary lipid binding can form a new class of magnetic nanoparticle-lipid microfilaments with unprecedented flexibility and self-healing properties. In the presence of a uniform magnetic field, the magnetophoretic attraction of the particles combined with interparticle dipole-dipole attraction drives the microfilament assembly. The fluid like lipid layer on the particles leads to stickiness on the surface of the filaments and the magnetic field concentration overcomes the potential electrostatic repulsion in the water phase. The lipid capillary bridges formed between the particles facilitate their permanent binding and sustain the flexible microfilament structure. We demonstrate that this surface stickiness combined with the magnetic response of the filaments can be used further to twist, bend and bundle the microfilaments into unusual structures.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich. This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively. Photoresponsive surfactant system based on fatty acids has been developed by the introduction in aqueous solution of a photoacid generator (PAG). Self-assembly transitions are triggered by UV irradiation due to a pH change induced by the presence of PAG.

International audience; Remarkable properties have emerged recently for aqueous foams including ultrastability and responsiveness. Responsive aqueous foams refer to foams for which the stability can be switched between stable and unstable states with a change in environment or with external stimuli. Responsive foams have been obtained from various foam stabilizers such as surfactants, proteins, polymers and particles and with various stimuli. Different strategies have been developed to design this type of soft materials. We briefly review the two main approaches used to obtain responsive foams. The first approach is based on the responsiveness of the interfacial layer surrounding the gas bubbles leading to responsive foams. The second one is based on the modifications occurring in the aqueous phase inside the foam liquid channels to tune the foam stability. We will highlight the most sophisticated approaches which use light, temperature and magnetic field leading to switchable foam stability.

International audience; Dough liquor (DL) is considered as a good model of bread dough liquid phase which plays an important role in alveolar structure creation. In this work, DL was extracted from dough pieces of various contents (g for 100 g flour) of water (55-70), sugar (0-15), rapeseed oil (0-10) and bran (0-20). The extraction yield of DL was 5.0 +/- 2.4% and its dry matter content varied between 10.8 and 27.2% of total DL mass. Its composition has been determined in terms of lipids content (

US National Science Foundation (NSF) Triangle MRSEC on Programmable Soft Matter DMR-1121107 US Army Research Office (ARO) W911NF-15-1-0115 NSF DMR-1122483 DMR-1309892 DMR-1436201 National Institutes of Health (NIH) P01-HL108808 1UH2HL123645; International audience; The fabrication of multifunctional materials with tunable structure and properties requires programmed binding of their building blocks(1,2). For example, particles organized in long-ranged structures by external fields(3,4) can be bound permanently into stiff chains through electrostatic or van der Waals attraction(4,5), or into flexible chains through soft molecular linkers such as surface-grafted DNA or polymers(6-11). Here, we show that capillarity-mediated binding between magnetic nanoparticles coated with a liquid lipid shell can be used for the assembly of ultraflexible microfilaments and network structures. These filaments can be magnetically regenerated on mechanical damage, owing to the fluidity of the capillary bridges between nanoparticles and their reversible binding on contact. Nanocapillary forces offier opportunities for assembling dynamically reconfigurable multifunctional materials that could find applications as micromanipulators, microbots with ultrasoft joints, or magnetically self-repairing gels.

International audience; Fatty acids are anionic surfactants under their deprotonated forms. They are surfactants with both biodegrability and low toxicity. Fatty acid molecules can self-assemble under various shapes in aqueous solution. These self-assembled structures can respond to stimuli such as pH, CO2 and temperature due to changes occurring at the molecular level. These specificities make them surfactants of special interest to tune the properties at the macroscopic scale. The aim of this article is to review the recent advances in the creation and in the understanding of responsive self-assemblies obtained from fatty acid molecules in aqueous solution. The links between the microscopic, mesoscopic and macroscopic scales are described. The alkyl chain melting phenomenon triggered by temperature at the molecular level leading to thermoresponsive interfaces and foams at the macroscopic scale is highlighted.

International audience; In this article, we show that stimuli-induced microscopic transformations of self-assembled surfactant structures can be used to tune the macroscopic bulk and interfacial rheological properties. Previously, we had described the formation of micron-sized 12-hydroxystearic acid tubes having a temperaturetunable diameter in the bulk, and also adsorbing at the air-water interface. We report now a detailed study of the bulk and interfacial rheological properties of this solution of thermoresponsive tubes as a function of temperature. In the bulk, the structural modifications of tubes with temperature lead to sharp and non-monotonous changes of rheological behavior. As well, at the air-water interface, the interfacial layer is shifted several times from rigid-like to fluid-like as the temperature is increased, due to morphological changes of the adsorbed interfacial layer. The temperature-induced variations in the fatty acid supramolecular organization and the richness in structural transitions at this microscopic level lead to unique rheological responses in comparison with conventional surfactant systems. Also, this study provides new insights into the required packing conditions for the jamming of anisotropic soft objects and highlights the fact that this system becomes glassy under heating. Due to these unique macroscopic properties both in the bulk and at the interface, this simple system with stimuli-responsive viscoelasticity is of interest for their potential applications in pharmacology or cosmetic formulations.

International audience; Fatty acids can self-assemble under various shapes in the presence of amines or cationic components. We assemble and compare these types of self-assembly leading toward a catanionic system either with a cationic surfactant or with an amine component playing the role of counter-ion. First, we focus on the molar ratio as a key driving parameter. Known and yet un-known values from other quantities governing the colloidal properties of these systems such as structural surface charge, osmotic pressure, molecular segregation, rigidity, in plane colloidal interactions and melting transition are discussed. We include also recent results obtained on the interfacial and foaming properties of these systems. We will highlight the specificity of these self-assemblies leading to unusual macroscopic properties rich of robust applications.

International audience; Aqueous foams are formed of air bubbles dispersed in a water phase. Despite the simplicity of these ingredients, the resulting foams can have an impressive range of material properties. In this review, an overview will be given on recent results obtained on the foaming properties of particles, self-assembled and aggregated structures. We will highlight how the presence of objects inside the foam can drastically modify the foam stability from unstable to ultrastable. (C) 2014 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

The organization and functional properties of caseins are influenced by several factors like temperature, pH, ionic environment, ionic strength, casein type and organization. The objective of this work was to prepare suspensions of casein micelles with different mineralization states to study their new physico-chemical and foaming properties. The different suspensions were obtained after milk acidification at various pH values (6.7 as control and 6.4, 6.1, 5.8 and 5.5) and then dialyzed against milk ultrafiltrate to have similar pH values and ionic environment. Each suspension was characterized in terms of i. composition and distribution of minerals and casein molecules between continuous and colloidal phases, ii. physico-chemical characteristics (percentage of sedimentable material, turbidity, particle size distribution, state of aggregation of casein molecules, shape, charge and hydration) and iii. foaming properties (foaming capacity and foam stability). The obtained suspensions were progressively demineralized and partial dissociations of casein micelles were observed. The dissociated part corresponded to non-sedimentable particles by ultracentrifugation. These particles have average diameter of about 20–35 nm and molecular weight between 106 and 107 g mol−1. The proportion of this population smaller in size increased when the pH used to obtain the different casein suspensions was acid (6.7