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International audience; From the 15 th century onwards, painters began to treat their oils with lead compounds before grinding them with pigments. Such a treatment induces the partial hydrolysis of the oil triglycerides and the formation of lead soaps, which significantly modify the rheological properties of the oil paint. Organization at the supramolecular scale is thus expected to explain these macroscopic changes. Synchrotron Rheo-SAXS (Small Angle X-Ray Scattering) measurements were carried out on leadtreated oils, with different lead contents. We can now propose a full picture of the relationship between structure and rheological properties of historical saponified oils. At rest, lead soaps in oil are organized as lamellar phases with a characteristic period of 50 Å. Under shear, the loss of viscoelastic properties can be linked to the modification of this organization. Continuous shear resulted in a preferential and reversible orientation of the lamellar domains which increased with the concentration of lead soaps. The parallel orientation predominates over the entire shear range (0-1000 s-1). Conversely, oscillatory shear coiled the lamellae into cylinders that oriented themselves vertically in the rheometer cell. This is the first report of such a vertical cylindrical structure obtained under shear from lamellae.

International audience; The two paintings Infant Bacchanals (Museo Nazionale d’Arte Antica, Palazzo Barberini, Rome, Italy) executed by Nicolas Poussin (Les Andelys, 1594–Rome, 1665) in around 1626 are thought to have been painted “a guazzo”, which means either with a glue or with an egg binding medium. To date, this has never been confirmed through analysis. Dual-beam time-of-flight secondary ion mass spectrometry (TOF-SIMS), using a bismuth cluster liquid metal ion gun and an argon gas cluster ion beam, allows the mapping of organic and inorganic matter on paintings cross sections, with the possibility to acquire submicrometer-resolution mass spectrometry images of the sample, together with high mass resolution using a delayed extraction of secondary ions. The surfaces of cross sections from both paintings were prepared beforehand either by polishing or by microtome cutting and then cleaned with the gas cluster ion beam directly inside the vacuum chamber of the instrument. The nature of the binders in the two paintings was investigated by TOF-SIMS analyses. By considering the uneven physical properties of the heterogeneous analyzed surfaces, several high-resolution images were recorded with different instrument settings. The detection of lipids seems to point toward an oil-containing medium, rather than a glue-binding medium. An emulsion made of oil and glue is another hypothesis to be explored to better understand the artist’s working methods in his early career.

International audience; Scanning macro-XRF, XRF point measurements and hyperspectral reflectance imaging in the visible and near-infrared range were combined to characterize the pigments of a Tibetan painting. The complementary use of the different investigation techniques allowed us to (i) clearly identify the pigments used by the artist, (ii) strengthen the few data present in historical and contemporary sources and (iii) provide data necessary for any accurate conservation treatment of the painting. The proposed methodology allows an in-depth characterization of the materials used in thangkas, with the identification of all the pigments used by Tibetan artists, as shown by the analyses of reference samples. In the present study traditional pigments, commonly cited in historical sources, were identified such as vermilion, minium, orpiment and azurite, but also more unusual compounds such as brochantite and antlerite (in blue/green areas). Elemental distribution images confirmed that some parts of the thangka were restored, without taking into account the original pigments or the original design. Underlying annotations and a carbon black under-drawing were highlighted by the application of near-infrared hyperspectral imaging technique, which proved to be particularly useful for the study of such paintings.

Gelled mediums were widely used during the nineteenth century, added to paint on the palette to modify its rheological, optical, and drying properties. Many variations of gelled mediums exist in the literature, all with the common basis of mastic resin or varnish, drying oil, and a lead compound. With the aim of unveiling the chemistry of such systems, reconstructions were carried out not only following the historical recipes, but in addition, exploring variations and simplifications to get a better understanding of the key ingredients and interactions inducing gelation. Different parameters were tested to establish whether these have an impact on the gelation mechanisms, particularly the influence of the nature and proportions of the ingredients and the preparation process. These reconstructions and their FTIR characterisation reveal the formation of metal-resin soaps, but also underline the specific role of lead in the gelation.

If ancient written sources and the visual analysis of polychromies have recently revealed the complexity of the technique of painting on statues and their frequent restoration, the non-invasive punctual chemical analyses carried out do not allow one to access the chemical composition of the different paint layers. This paper presents the analysis of three statues from Roman Africa discussing the results obtained from this understudied territory and chronology. By combining visual observation (VIS, UVL), video microscopy and MA-XRF imaging, we propose here a non-invasive protocol to determine the chemical composition of the different paint layers. This allows one to unveil the complexity of the ‘know-how’ of a sculpture painter and sheds light on the evolution of the original appearance of the statues.

International audience; Egg-tempera painting is a pictorial technique widely used in the Middle Ages, although poorly studied in its physico-chemical aspects until now. Here we show how NMR relaxometry and rheology can be combined to probe egg-tempera paints and shed new light on their structure and behavior. Based on recipes of the 15th century, model formulations with egg yolk and green earth have been reproduced to characterize the physicochemical properties of this paint at the mesoscopic and macroscopic scales. The rheological measurements highlight a synergetic effect between green earth and egg yolk, induced by the interactions between them and the structural organisation of the system. 1H NMR relaxometry emphasizes the presence and the structure of a network formed by the yolk and the pigment.

Lead white, composed of a mixture of cerussite and hydrocerussite (respectively PbCO3 and Pb3(CO3)2(OH)2), is often associated in paintings with other white pigments, especially calcite. By combining in-situ analyses with paint reconstructions, we attempt to get a better understanding of the role of this addition of calcite and to investigate how artists may have used it to modify the properties of their paints. Lead-based white pigments of a Dutch 17th-century nuancier have been analysed as well as historical paintings. Two examples are given: one from a painting by Roger van der Weyden, in the 15th century, and one by Nicolas Poussin, in the 17th century, from specific zones that indicate the addition of calcite. The presence of calcite and pigments enhances both the optical and the rheological properties. Visible reflectance spectroscopy was carried out on pure paints as well as mixtures and indicated an increase in the transparency of the paint mixture in comparison to pure lead white. Rheological measurements also indicated an increase in the elastic and viscous moduli, as well as of the yield stress again in comparison to pure lead white. Calcite could thus have been used to assist in the creation of impasto effects in lead white paints.

The material evidence for the wax finish on ancient marble statues, known as ganosis, is scarce and controversial, although Greek and Latin sources describe the recipes and cultural value of this treatment. The surface treatment of a colossal Roman head from the Roman theatre of Dougga (Tunisia), dated to the end of the second century CE, is studied by a multi-analytical protocol (video-microscope, cross section, and time-of-flight secondary ion mass spectrometry of one sample). The results of this physico-chemical analysis and the comparison with ancient recipes, prove the use of ganosis on a Roman statue and explore, for the first time, the application of the recipes described in ancient sources. This result shows the potential of the Time-of-Flight Secondary Ion Mass Spectrometry analysis, detecting at the same time organic and inorganic materials and their stratigraphy, to study the ancient recipes.

International audience; Hypothesis: The objective is to elucidate the multiscale dynamics of water within natural mixtures of minerals, green earth pigments that are mainly composed of phyllosilicates containing large amount of iron. In particular, the interaction of water with the different kinds of surfaces has to be probed. One issue is to examine the influence of surface type, basal or edge, on the dispersion quality.Experiment: The study was carried out using 1H variable field NMR relaxometry on various green earth pigment dispersions and concentrations. To analyse the data, a new analytical model was developed for natural phyllosilicates containing large amount of paramagnetic centres.Finding: The proposed theoretical framework is able to fit the experimental data for various samples using few parameters. It allows to determining water diffusion and residence times in complex phyllosilicate dispersions. Furthermore, it makes it possible to differentiate the contribution of the basal and edge surfaces and their respective surface area in interaction with water. Moreover, NMR relaxation profile reveals to be highly sensitive to the structural aspect of the phyllosilicates and to the accessibility of water to iron, hence allowing to discriminate clearly between two very similar phyllosilicates (glauconite and celadonite) that are difficult to distinguish by standard structural methods.

International audience; Lead white was a white pigment extensively used in paintings from Antiquity until the beginning of the 20th century. It is composed of hydrocerussite (Pb3(CO3)2(OH)2) and cerussite (PbCO3). Historical recipes report metallic lead, vinegar and horse manure as ingredients to produce the two lead carbonates. The incorporation of organic CO2 carrying 14C representative of the time of manufacture of lead white allows radiocarbon dating of this pigment. One possible protocol for lead white paint preparation for dating is based on the extraction of carbon from lead carbonates by thermal decomposition. Since lead white paints are mixed with a binder and other pigments, a thermogravimetric study was implemented to study CO2 extraction from each component. The measurements were carried out on samples of modern paints prepared with lead white (lead carbonate), Meudon white (calcium carbonate) and linseed oil. The results show that it is possible to separate the carbon of interest (carrying the 14C signature: lead white and linseed oil) from the dead carbon coming from geological carbonates (containing no radiocarbon: Meudon white) by heating the paint sample at 400 °C. This study provides a better understanding of the thermal behavior of these three paint constituents and confirms the validity of the thermal protocol for the preparation of lead white paints for radiocarbon dating.

International audience; The Alcazar Palace (Seville, Spain) is famous for its ceramic decorations; 16 th century wall tiles of different typologies have been analyzed in order to relate the manufacturing process of their colored glazes to the evolving technologies of the Renaissance. Chemical and mineralogical compositions have been determined in situ by non-destructive X-ray fluorescence (XRF) and X-ray diffraction (XRD) on arista ceramics in the Cenador de Carlos Quinto, and majolica ceramics in the Palacio Gotico and the Royal oratory. The arista style belongs to the local Hispano-Moresque ceramic tradition. Majolica tiles have the complex microstructures of glazes from Italy. The two types are clearly differentiated by their typology, morphology (curved vs flat surface), and also microstructure (single vs multi-layers), glaze chemistry, and use of different coloring agents. Moreover, we found different glaze chemistries in the investigated majolicas, which correspond to different artists and/or practices.

International audience; British 19th century painters formulated gelled systems often described as ideal paint mediums. These so-called megilps or gumtions are based on common paint materials like linseed oil, lead acetate, and mastic resin, and allowed painters such as J.M.W Turner to improve their paint's properties and achieve unprecedented effects in an age of innovation. To propose a structural scheme of these hybrid systems of unprecedented complexity, it is paramount to design and study model systems using a broad combination of advanced spectroscopic techniques and microscopies. Through this approach, gel Mediums can be described as nanocomposites based on lead metallogels co-existing with lead oxide nanoparticles and a partially polymerized fraction. These functional hybrid materials created a real breakthrough on 19th century paints performances.

Colour was a key feature of Greek and Roman sculpture, but due to the current bare-marble appearance of many such statues, it is now frequently overlooked. This is illustrated here by the first study of polychromy in Roman statues from the province of Africa Proconsularis. Five sculptural fragments dating to the second and third centuries AD were examined using techniques including XRF analysis, and a variety of pigments were detected. The differing colour schemes presented by each of the pieces are here assessed, and consideration is given to the technical process by which they were coloured, the significance of their decoration and the potential for applying similar approaches in future studies of ancient statuary.

Recipes describing the controlled mixture and reaction of fat/oil with lead-based compounds have been known and employed since antiquity until modern times. Two major fields have developed such practices: pharmacy, for the preparation of lead plasters (i.e., dressings made of lead-based compounds and fat/oil) and related unguents, and painting, for the preparation of thickened oils. Here, we review and analyze a set of almost 500 recipes, from historical texts from the Mediterranean area, dating from Pharaonic Egypt to the nineteenth century. Recipes show similarities (e.g., type of lead ingredients, advice regarding the grinding level of powders, risks associated with overheating the mixtures) and differences (e.g., type of fat/oil, introduction of additional compounds, use of sunlight) which can be explained by the different purposes and applications of the formed pastes: plasters must be soft, with a thick consistency, and adhere to the skin for a long time without drying; conversely, “thickening” oil by reaction with lead-based compounds is intended mainly to speed up drying reactions in paintings. Also, some historical evolutions may be noticed, e.g., the choice of lead ingredients and the progressive replacement of lead-based compounds by zinc oxide for toxicological reasons, the interpretation in chemical terms (in particular the identification of the formed lead soaps and glycerol), and, for lead plasters, the quasi-systematic introduction of water from the eighteenth century and the standardization of recipes.

International audience; Hybrid materials based on montmorillonite, a cationic polymer and carminic acid were prepared. The surface charge of montmorillonite was inversed thanks to the cationic polymer, polydiallyldimethylammonium chloride. Samples were characterized by a set of different techniques including Infrared (IR) and Nuclear Magnetic Resonance (NMR) spectroscopies to highlight the nature of the interactions between the organic and inorganic parts. The photo-stability of the samples was tested for different durations, and L*a*b* parameters were measured. It was possible to propose an approach for the degradation mechanism of the supported dye thanks to EPR (electron paramagnetic resonance) spectroscopy. The experimental data were in agreement with the theoretical periodic DFT calculations where a molecular scheme of the adsorption complex was proposed, and the importance of hydration on the stability of the adsorption complex highlighted.

Hybrid materials based on one organic dye, the carminic acid, and montmorillonite have been prepared and characterized by a multi-technical approach. Aluminum and tin II cations were used in the experimental mixtures in order to have a chelating effect with the carminic acid. X-Ray diffraction patterns (XRD) did not highlight any intercalation of the organic molecule in the interlayer space, a result confirmed by transmission electron microscopy (TEM) micrographs. The fixation of the organic molecules on the phyllosilicates was then investigated by 13 C solid state nuclear magnetic resonance (NMR) and time resolved fluorescence spectroscopies. The spectra showed the role that the ketone and catechol functions of the dye played for its fixation and stressed on the decrease of its mobility when the lake pigment was formed. The role of the clay edges and/or surface was highlighted by this set of experimental data.

L’utilisation des techniques d’imagerie chimique pour l’etude des peintures d’art est en plein essor. Ces techniques non invasives et mobiles permettent l’acquisition d’un grand nombre de donnees spatiales et spectrales, dont l’interpretation ouvre de nombreuses perspectives pour regarder autrement les oeuvres d’art. Nous presentons ici les concepts et les applications de deux techniques : l’imagerie par spectrometrie de fluorescence X et l’imagerie hyperspectrale en lumiere visible et proche infrarouge.

International audience; Green earth is a common green pigment based on celadonite and glauconite, used since Antiquity by artists. Two geological minerals, eight commercial green earth pigments and a sample taken from a historical location in Monte Baldo were characterized. A set of different techniques including X-Ray diffraction (XRD), scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS) and numerous spectroscopies: spectrophotocolorimetry, near and mid infrared, Raman, Mössbauer were used to identify the structure and composition of the different earths. The results highlight complex composition with the presence of various phases, which can be due to the pigment sampling at a different location in the same deposit. Mobile and non-invasive analyses were carried out in order to suggest a protocol for the identification of green earth in artworks, and more specifically to distinguish celadonite and glauconite. With the available mobile non-invasive techniques, and the above analyses on the raw pigments, the green area in Nicolas Poussin’s painting, Bacchanales d’enfants (Galleria Nazionale d’Arte Antica (GNAA), Rome) was examined as a case study.

Of the once colourful decoration of antique Greek statues only few traces remain today. But these allow one to reconstruct part of the polychromy, based on visual and microscopic inspection and spot analysis with spectroscopic methods. For the first time we used mobile hyperspectral reflectance imaging in the visible and near infrared range and scanning macro XRF imaging for the investigation of remnants of antique polychromy on a stationary object. With this method of analysis we were able to reveal previously unknown traces of ancient paint on the Frieze of the Siphnian Treasury (around 525 BCE). This illustrates the capabilities of this techniques to obtain new insights in a well-described and investigated object. Further, we gained insight into the painting technique, involving an earth based preparation layer. Finally, we present an alternative way to the treatment of the hyperspectral reflectance data in order to obtain easily readable pigment distribution images in case of heterogeneous illumination.

Through the paintings of the old masters, we showcase how materials science today provides us with a vision of the processes involved in the creation of a work of art: the choice of materials, the painter's skill in handling these materials, and the perception of the finished work.

International audience; We present here the combination of in situ non invasive techniques to investigate a precious 15th century illuminated manuscript of Petrarch’s work, De remediis utriusque fortunae held in the Méjanes library in Aix-en-Provence (France). X-Ray fluorescence spectroscopy, mapping and point analysis, and visible reflectance hyperspectral imaging allow an unprecedented analysis of this manuscript. They provide new clues for its attribution by revealing a partly hidden coat of arms and describing the illuminator’s palette and techniques in detail. We reveal the identity of the first possessor of this manuscript, Tanguy IV du Châtel, known as a 15th century bibliophile close to Louis XI. This information is a further element contributing to the attribution of the richly illuminated folio 6 of this manuscript to François Le Barbier. Pigments and dyes used for this folio have been investigated with particular emphasis on the study of the superimposed colours thus providing a better understanding of the artist’s technique and know-how.

International audience; British 19th century painters such as J.M.W. Turner, commonly modified the properties of their paint by using gels called 'gumtions'. These gels allowed them to easily tune the paint handling and drying properties. The fascinating properties of these 'gumtions' were obtained by adding lead acetate to a ternary system based on mastic resin, linseed oil and turpentine. Herein, we report and investigate in depth the rheological properties of these gels as well as their structure at a molecular and supra-molecular scale.

A nonproprietary software package, "PyMca", primarily developed for X-ray fluorescence analysis offers an easy-to-use interface for calculating maps, by integrating intensity (of X-ray fluorescence, as well as any spectral data) over Regions Of Interest (ROI), by performing per pixel operations or by applying multivariate analysis. Here we show that, while initially developed to analyze hyperspectral two-dimensional (spatial) maps, this tool can be beneficial as well to anyone interested in measuring spectral variations over one or two dimensions, these dimensions being time, temperature, and so on. Different possibilities offered by the software (preprocessing, simultaneous analysis of replicas, of different conditions, ROI calculation, multivariate analysis, determination of reaction rate constant and of Arrhenius plot) are illustrated with two examples. The first example is the Fourier transform infrared spectroscopy (FTIR) follow-up of the saponification of oil by lead compounds. The disappearance of reagent (oil) and formation of products (lead carboxylates and glycerol) can be easily followed and quantified. The second example is a combined extended X-ray absorption fine structure (EXAFS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and mass spectroscopy (MS) analysis of RhAl2O3 catalyst under NO reduction by CO in the presence of O2. It is possible to appreciate, in a single shot, Rh particles' structure and surface changes and gas release and adsorption in the reaction conditions.

The perfection of Leonardo da Vincis painting technique hasalwaysbeenfascinating.Thegradationoftonesorcolorsfromlight to dark is barely perceptible. Neither brushstroke norcontourisvisible:lightsandshadesareblendedinthemannerof smoke. Understanding this technique, usually calledsfumato, remains one of the challenges still unaddressed inart history. Herein we show that quantitative X-ray fluores-cence spectroscopy performed directly on the works of artmakes it possible to access the description of the paint layersused in the flesh tones. We determined the composition andthe thickness of the paint layers of nine faces, painted byLeonardo (or attributed to him) over 40 years of his activity.Theresultsshednewlightonhisconstantresearchtoimprovethe visual aspects of his works of art. In his later paintings, hewas able to apply translucent layers (glazes), which weremainly composed of an organic medium in very thin films,down to a micrometer scale.How did Leonardo da Vinci obtain such impressivenaturalistic effects in his paintings? The description of themasters sfumato technique is the subject of active discussionin arthistory.

Rheology is the science of flow, which is a phenomenon found in every painting operation, such as decorative paintings or protective coatings. In this article, the principles of rheology as applied to paintings and coatings are recalled in a first part and the rheological criteria required in the paint industry presented. Indeed, different flow behaviours leads to different finishes. The same procedure and techniques as in industry can be employed to explain some evolutions in oil painting aspects over the centuries. The first recipes for oil painting indicate the use of treated oil, resins and spirits. This article deals with the evolution of the composition of these systems as media for oil painting, according to rheological clues. During the Renaissance period, the media used were Newtonian or slightly shear thinning and allowed one a perfect levelling. Then techniques changed, paints became more opaque with less addition of oil/resin media, and brushstrokes appeared visible. Some preparations containing lead, oil and mastic resin, whose flow behaviour is closed to those required in industry, may have appeared during the 17th century and are still used and sold today. To cite this article: L. de Viguerie et al., C. R. Physique 10 (2009).

The glaze technique, which appeared with the oil painting, has permitted a real improvement in the aspect of Renaissance paintings. A better understanding of this technique, which made the smile of Mona Lisa so famous, and especially of the composition and the properties of the various materials used is necessary to improve the conservation and restoration of art works. Historical sources have been investigated to list the possible glaze recipes. If raw oil can be used, in most cases, the oil is modified, thickened in the sun or treated with a lead compound. Additives can also improve the medium properties and many recipes indicate the common addition of varnish to the oil for glaze medium preparation. This paper describes the reconstitution of two formulation procedures: the mixture of mastic resin, turpentine and raw oil, and the heating of oil with lead oxide. The flow behaviour of these media is then investigated. These rheological data were used to discuss their brushing and levelling properties which are of great interest for glaze media. The ratio of the various ingredients in the mixture of resin, oil and turpentine can be adjusted by the painter to reach the required viscosity on the palette, but it does not change the general behaviour of these mixtures. On the contrary, the rheological behaviour of the glaze medium can be modified by the treatment of the oil with lead oxide. The saponification induced by this procedure leads to shear thinning mixtures, with higher viscosities. No difference is seen depending on the nature of the drying oil whereas the addition of water during the heating process has a real influence on the flow behaviour of the medium. This analysis provides first clues for the reconstruction of the glaze medium formulation.

X-ray fluorescence spectrometry (XRF) allows a rapid and simple determination of the elemental composition of a material. As a non-destructive tool, it has been extensively used for analysis in art and archaeology since the early 1970s. Whereas it is commonly used for qualitative analysis, recent efforts have been made to develop quantitative treatment even with portable systems. However, the interpretation of the results obtained with this technique can turn out to be problematic in the case of layered structures such as easel paintings. The use of differential X-ray attenuation enables modelling of the various layers: indeed, the absorption of X-rays through different layers will result in modification of intensity ratio between the different characteristic lines. This work focuses on the possibility to use XRF with the fundamental parameters method to reconstruct the composition and thickness of the layers. This method was tested on several multilayers standards and gives a maximum error of 15% for thicknesses and errors of 10% for concentrations. On a painting test sample that was rather inhomogeneous, the XRF analysis provides an average value. This method was applied in situ to estimate the thickness of the layers a painting from Marco d’Oggiono, pupil of Leonardo da Vinci.

The present study investigates the deposition of hybrid organic/inorganic monolayers composed of polyoxometalate (POM) of the Keggin-type [PW12O40]3− electrostatically linked to three alkylammonium surfactants. The surface pressure dependence, i.e. Langmuir isotherm, as well as their 2D self-assembly has been investigated with mono- and double-chained surfactants and by varying the alkyl chain length. Stable monolayers were obtained for the hexadecyltrimethylammonium and the didodecyldimethylammonium POM surfactants, called respectively C16POM and 2C12POM. It was found that increasing the surface pressure led to the formation of crystallized nano- and micro-domains in coexistence with the monolayer. The crystallites formed were monodisperse in their size repartition and showed various shapes and sizes: oblate nanoparticles of nanometric size (height ca. 7 nm, diameter ca. 140 nm) for C16POM and micrometric 2D-hexagonal crystallites for 2C12POM. The monolayers and the micro-(nano-) crystallites have been characterized after transfer on silicon wafers by means of atomic force microscopy (AFM), transmission electron microscopy (TEM) and surface-enhanced ellipsometric contrast (SEEC). High crystallinity of the hexagonal aggregates was revealed by electron diffraction (ED). For 2C12POM the monolayer formed before crystallisation is in a 2D-liquid state with the alkyl chains pointing out of the water with an average angle of the alkyl chains to the normal of the plane estimated at 50°. It is shown that the surface pressure induced crystallization of the POM surfactant results in the change of the ammonium surfactant arrangement around the POM with the alkyl chains pointing up and down the POM units showing a reverse bilayer-like structure. This change in the ammonium surfactant arrangement in response to the increase of the surface pressure enables (i) to reduce the molecular area and (ii) the formation of a 2D-hexagonal crystalline lattice of POM units. On the other hand for C16POM the formation of oblate nanoparticles is driven by a three-dimensional growth at the water surface.

As semifluorinated alkanes (SFA) present an unusual class of mesogenic units for supramolecular structure formation, the study of their physical properties and self-assembly at fluid interfaces is of substantial relevance. To this end, the two-dimensional phase behavior and the viscoelastic properties of semifluorinated alkanes with symmetric number of carbon atoms in the fluorinated and hydrogenated side chains (F(CF2)12–(CH2)12H and F(CF2)11CH2–core–(CH2)12H with dibromophenyl core were investigated at the air/water interface and compared to the asymmetric F(CF2)12(CH2)20H system. Surface pressure/area isotherms and compression–expansion cycles were recorded at 20 °C, 40 °C, and 50 °C. Depending on the molecular details, an unexpected phase transition and hysteresis in compression–expansion cycles could be observed. Interfacial rheology revealed for all monolayer systems a solid-like viscoelastic response over the investigated range of surface pressures. The interfacial storage modulus G′i and interfacial loss modulus G′′i increased with increasing surface pressure. More importantly, at constant surface pressure the simple semifluorinated alkanes, forming nearly circular 2D micellar structures at the interface, exhibited rheological properties reminiscent of glass-like colloid systems. On the other hand, the SFA with the dibromophenyl core formed 2D interfacial micelles of highly elongated shape with dendritic domains and exhibited gel-like rheological properties, similar to those of the asymmetric alkane. Moreover, with increasing surface pressure the response of the asymmetric system alters from glassy to gel-like. These findings suggest that fine differences in the molecular structure are reflected in the linear viscoelastic response of the Langmuir films, and hence offer the possibility to molecularly tune the rheology of fluid interfaces.

International audience; ConspectusThe chemical study of materials from natural history and cultural heritage, which provide information for art history, archeology, or paleontology, presents a series of specific challenges. The complexity of these ancient and historical materials, which are chemically heterogeneous, the product of alteration processes, and inherently not reproducible, is a major obstacle to a thorough understanding of their making and long-term behavior (e.g., fossilization). These challenges required the development of methodologies and instruments coupling imaging and data processing approaches that are optimized for the specific properties of the materials. This Account discusses how these characteristics not only constrain their study but also open up specific innovative avenues for providing key historical information. Synchrotron methods have extensively been used since the late 1990s to study heritage objects, in particular for their potential to provide speciation information from excitation spectroscopies and to image complex heritage objects and samples in two and three dimensions at high resolution. We examine in practice how the identification of key intrinsic chemical specificities has offered fertile ground for the development of novel synchrotron approaches allowing a better stochastic description of the properties of ancient and historical materials. These developments encompass three main aspects: (1) The multiscale heterogeneity of these materials can provide an essential source of information in the development of probes targeting their multiple scales of homogeneity. (2) Chemical alteration can be described in many ways, e.g., by segmenting datasets in a semiquantitative way to jointly inform morphological and chemical transformation pathways. (3) The intrinsic individuality of chemical signatures in artifacts triggers the development of specific strategies, such as those focusing on weak signal detection. We propose a rereading of the advent of these new methodologies for analysis and characterization and examine how they have led to innovative strategies combining materials science, instrument development, history, and data science. In particular, we show that spectral imaging and the search for correlations in image datasets have provided a powerful way to address what archeologists have called the uncertainty and ambiguity of the material record. This approach has implications beyond synchrotron techniques and extends in particular to a series of rapidly developing approaches that couple spectral and spatial information, as in hyperspectral imaging and spatially resolved mass spectrometry. The preeminence of correlations holds promise for the future development of machine learning methods for processing data on historical objects. Beyond heritage, these developments are an original source of inspiration for the study of materials in many related fields, such as environmental, geochemical, or life sciences, which deal with systems whose alteration and heterogeneity cannot be neglected.

The chemical composition of sandarac resin and its principal component communic acid was investigated by gas chromatography-mass spectrometry (GC-MS), MALDI-TOF (Matrix Assisted Laser Desorption Ionization - Time of Flight), ESI (Electrospray ionization)-Orbitrap, FTIR/ATR (Fourier transform infrared spectroscopy/Attenuated total reflectance), liquid- and solid state NMR (Nuclear magnetic resonance) spectroscopy. Six compounds with labdane and pimarane skeletons were identified in the commercial resin. The obtained mass spectra were interpreted and the mass spectrometric behaviour of these diterpenoids under EI conditions was described. Quantitative analysis by the method of internal standard revealed that identified diterpenoids represent only 10–30% of the analysed sample. The complexity of the reticulated fraction of the commercial sandarac resin was well reflected by the MALDI-TOF and ESI-Orbitrap mass spectra. As a result, MALDI-TOF mass spectra comprised three clusters of peaks in the m/z range of 300–900, and for the ESI-Orbitrap mass spectra contained five clusters of peaks in the m/z range of 300–1100. The peaks in the clusters corresponded to the oxygenated derivatives of the diterpenoids. The results obtained from the IRCP (Inversion Recovery Cross-Polarization) experiments revealed the rigid character of the sandarac resin samples analyzed and justified the hypothesis that the rest of the sample, which could not be quantified by the method of internal standard, would have a polymeric nature.; La composition chimique de la résine sandaraque et de son composant principal l’acide communique a été étudiée par chromatographie en phase gazeuse – spectrométrie de masse (GC-MS), MALDI-TOF (désorption-ionisation laser assistée par matrice - temps de vol), ESI (ionisation par électronébuliseur) - Orbitrap, FTIR/ATR (spectroscopie infrarouge à transformée de Fourier/réflectance totale atténuée), spectroscopie de RMN (résonance magnétique nucléaire) à l'état solide et liquide. Six composés avec des squelettes labdane et pimarane ont été identifiés dans la résine commerciale. Les spectres de masse obtenus ont été interprétés et le comportement en spectrométrie de masse de ces diterpénoïdes dans les conditions de l’impact électronique a été décrit. L'analyse quantitative par la méthode de l'étalon interne a révélé que les diterpénoïdes identifiés ne représentaient que 10 à 30% de l'échantillon analysé. La complexité de la fraction réticulée de la résine commerciale sandaraque est bien reflétée par les spectres de masse MALDI-TOF et ESI-Orbitrap. En conséquence, les spectres de masse de MALDI-TOF comprenaient trois clusters de pics dans la gamme m/z de 300-900, et ceux d’ESI-Orbitrap contenaient cinq clusters de pics dans la gamme m/z de 300-1100. Les pics dans les clusters correspondent aux dérivés oxygénés des diterpénoïdes. Les résultats obtenus à partir des expériences RMN par IRCP (Inversion Recovery Cross-Polarization) ont révélé le caractère rigide des échantillons de la résine sandaraque analysés et justifiaient l'hypothèse que le reste de l'échantillon, qui ne pouvait être quantifié par la méthode de l'étalon interne, aurait un caractère polymère.

The chemical composition of sandarac resin and its principal component communic acid was investigated by gas chromatography-mass spectrometry (GC-MS), MALDI-TOF (Matrix Assisted Laser Desorption Ionization - Time of Flight), ESI (Electrospray ionization)-Orbitrap, FTIR/ATR (Fourier transform infrared spectroscopy/Attenuated total reflectance), liquid- and solid state NMR (Nuclear magnetic resonance) spectroscopy. Six compounds with labdane and pimarane skeletons were identified in the commercial resin. The obtained mass spectra were interpreted and the mass spectrometric behaviour of these diterpenoids under EI conditions was described. Quantitative analysis by the method of internal standard revealed that identified diterpenoids represent only 10–30% of the analysed sample. The complexity of the reticulated fraction of the commercial sandarac resin was well reflected by the MALDI-TOF and ESI-Orbitrap mass spectra. As a result, MALDI-TOF mass spectra comprised three clusters of peaks in the m/z range of 300–900, and for the ESI-Orbitrap mass spectra contained five clusters of peaks in the m/z range of 300–1100. The peaks in the clusters corresponded to the oxygenated derivatives of the diterpenoids. The results obtained from the IRCP (Inversion Recovery Cross-Polarization) experiments revealed the rigid character of the sandarac resin samples analyzed and justified the hypothesis that the rest of the sample, which could not be quantified by the method of internal standard, would have a polymeric nature.; La composition chimique de la résine sandaraque et de son composant principal l’acide communique a été étudiée par chromatographie en phase gazeuse – spectrométrie de masse (GC-MS), MALDI-TOF (désorption-ionisation laser assistée par matrice - temps de vol), ESI (ionisation par électronébuliseur) - Orbitrap, FTIR/ATR (spectroscopie infrarouge à transformée de Fourier/réflectance totale atténuée), spectroscopie de RMN (résonance magnétique nucléaire) à l'état solide et liquide. Six composés avec des squelettes labdane et pimarane ont été identifiés dans la résine commerciale. Les spectres de masse obtenus ont été interprétés et le comportement en spectrométrie de masse de ces diterpénoïdes dans les conditions de l’impact électronique a été décrit. L'analyse quantitative par la méthode de l'étalon interne a révélé que les diterpénoïdes identifiés ne représentaient que 10 à 30% de l'échantillon analysé. La complexité de la fraction réticulée de la résine commerciale sandaraque est bien reflétée par les spectres de masse MALDI-TOF et ESI-Orbitrap. En conséquence, les spectres de masse de MALDI-TOF comprenaient trois clusters de pics dans la gamme m/z de 300-900, et ceux d’ESI-Orbitrap contenaient cinq clusters de pics dans la gamme m/z de 300-1100. Les pics dans les clusters correspondent aux dérivés oxygénés des diterpénoïdes. Les résultats obtenus à partir des expériences RMN par IRCP (Inversion Recovery Cross-Polarization) ont révélé le caractère rigide des échantillons de la résine sandaraque analysés et justifiaient l'hypothèse que le reste de l'échantillon, qui ne pouvait être quantifié par la méthode de l'étalon interne, aurait un caractère polymère.