Institut Charles Sadron

Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.

Fullerene single-wall nanotubes (SWNTs) were produced in yields of more than 70 percent by condensation of a laser-vaporized carbon-nickel-cobalt mixture at 1200degreesC. X-ray diffraction and electron microscopy showed that these SWNTs are nearly uniform in diameter and that they self-organize into "ropes," which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms. The x-ray form factor is consistent with that of uniformly charged cylinders 13.8 +/- 0.2 angstroms in diameter. The ropes were metallic, with a single-rope resistivity of <10(-4) ohm-centimeters at 300 kelvin. The uniformity of SWNT diameter is attributed to the efficient annealing of an initial fullerene tubelet kept open by a few metal atoms; the optimum diameter is determined by competition between the strain energy of curvature of the graphene sheet and the dangling-bond energy of the open edge, where growth occurs. These factors strongly favor the metallic (10,10) tube with C5v symmetry and an open edge stabilized by triple bonds.

Background During the last few decades, progress has been made in manipulating the architecture of synthetic polymer materials. However, the primary structure—that is, the sequential arrangement of monomer units in a polymer chain—is generally poorly controlled in synthetic macromolecules. Common synthetic polymers are usually homopolymers, made of the same monomer unit, or copolymers with simple chain microstructures, such as random or block copolymers. These polymers are used in many areas but do not have the structural and functional complexity of sequence-defined biopolymers, such as nucleic acids or proteins. Indeed, monomer sequence regulation plays a key role in biology and is a prerequisite for crucial features of life, such as heredity, self-replication, complex self-assembly, and molecular recognition. In this context, developing synthetic polymers containing controlled monomer sequences is an important area for research. Advances Various synthetic methods for controlling monomer sequences in polymers have been identified, and two major trends in the field of sequence-controlled polymers have emerged. Some approaches use biological concepts that have been optimized by nature for sequence regulation. For instance, DNA templates, enzymes, or even living organisms can be used to prepare sequence-defined polymers. These natural mechanisms can be adapted to tolerate nonnatural monomers. The other trend is the preparation of sequence-controlled polymers by synthetic chemistry. In the most popular approach, monomer units are attached one by one to a support, which is an efficient method but demanding in practice. Recently, some strategies have been proposed for controlling sequences in chain-growth and step-growth polymerizations. These mechanisms usually allow fast and large-scale synthesis of polymers. Specific kinetics and particular catalytic or template conditions allow sequence regulation in these processes. Outlook The possibility of controlling monomer sequences in synthetic macromolecules has many scientific and technological implications. Information can be controlled at the molecular level in synthetic polymer chains. This opens up interesting perspectives for the field of data storage. In addition, having power over monomer sequences could mean structural control of the resulting polymer, as it strongly influences macromolecular folding and self-assembly. For instance, functional synthetic assemblies that mimic the properties of globular proteins, such as enzymes and transporters, can be foreseen. Moreover, monomer sequence control influences some macroscopic properties. For example, bulk properties such as conductivity, rigidity, elasticity, or biodegradability can be finely tuned in sequence-controlled polymers. The behavior of polymers in solution, particularly in water, is also strongly dependent on monomer sequences. Thus, sequence regulation may enable a more effective control of structure-property relations in tomorrow’s polymer materials.

A new type of nanocellulosic material has been prepared by high-pressure homogenization of carboxymethylated cellulose fibers followed by ultrasonication and centrifugation. This material had a cylindrical cross-section as shown by transmission electron microscopy with a diameter of 5-15 nm and a length of up to 1 microm. Calculations, using the Poisson-Boltzmann equation, showed that the surface potential was between 200 and 250 mV, depending on the pH, the salt concentration, and the size of the fibrils. They also showed that the carboxyl groups on the surface of the nanofibrils are not fully dissociated until the pH has reached pH = approximately 10 in deionized water. Calculations of the interaction between the fibrils using the Derjaguin-Landau-Verwey-Overbeek theory and assuming a cylindrical geometry indicated that there is a large electrostatic repulsion between these fibrils, provided the carboxyl groups are dissociated. If the pH is too low and/or the salt concentration is too high, there will be a large attraction between the fibrils, leading to a rapid aggregation of the fibrils. It is also possible to form polyelectrolyte multilayers (PEMs) by combining different types of polyelectrolytes and microfibrillated cellulose (MFC). In this study, silicon oxide surfaces were first treated with cationic polyelectrolytes before the surfaces were exposed to MFC. The build-up of the layers was monitored with ellipsometry, and they show that it is possible to form very well-defined layers by combinations of MFC and different types of polyelectrolytes and different ionic strengths of the solutions during the adsorption of the polyelectrolyte. A polyelectrolyte with a three-dimensional structure leads to the build-up of thick layers of MFC, whereas the use of a highly charged linear polyelectrolyte leads to the formation of thinner layers of MFC. An increase in the salt concentration during the adsorption of the polyelectrolyte results in the formation of thicker layers of MFC, indicating that the structure of the adsorbed polyelectrolyte has a large influence on the formation of the MFC layer. The films of polyelectrolytes and MFC were so smooth and well-defined that they showed clearly different interference colors, depending on the film thickness. A comparison between the thickness of the films, as measured with ellipsometry, and the thickness estimated from their colors showed good agreement, assuming that the films consisted mainly of solid cellulose with a refractive index of 1.53. Carboxymethylated MFC is thus a new type of nanomaterial that can be combined with oppositely charged polyelectrolytes to form well-defined layers that may be used to form, for example, new types of sensor materials.

In this review, we survey the diversity of structures and functions which are encountered in advanced self-assembled nanomaterials. We highlight their flourishing implementations in three active domains of applications: biomedical sciences, information technologies, and environmental sciences. Our main objective is to provide the reader with a concise and straightforward entry to this broad field by selecting the most recent and important research articles, supported by some more comprehensive reviews to introduce each topic. Overall, this compilation illustrates how, based on the rules of supramolecular chemistry, the bottom-up approach to design functional objects at the nanoscale is currently producing highly sophisticated materials oriented towards a growing number of applications with high societal impact.

The formation of a new kind of biocompatible film based on poly(l-lysine) and hyaluronic acid (PLL/HA) by alternate deposition of PLL and HA was investigated. Optical waveguide lightmode spectroscopy, streaming potential measurements, atomic force microscopy, and quartz crystal microbalance (QCM) were used to analyze the different aspects of the buildup process such as the deposited mass after each new polyelectrolyte adsorption, the overall surface charge of the film, and its morphology. As for “conventional” polyelectrolyte multilayer systems, the driving force of the buildup process is the alternate overcompensation of the surface charge after each PLL and HA deposition. The construction of (PLL/HA)n films takes place over two buildup regimes. The first one is characterized by the formation of isolated islands that grow both by addition of new polyelectrolytes on their top and by mutual coalescence of the islands. The second regime sets in once a continuous film is formed after the eighth layer pair deposition in our working conditions and is characterized by an exponential increase of the mass. QCM measurements at different frequencies evidenced a viscoelastic behavior of the films with a shear viscosity on the order of 0.1 Pa·s. This new kind of biocompatible film incorporating a natural polymer of the cartilage and a widely used polypeptide is of potential use for cell-targeted action.

Abstract The crystallization behavior after partial or complete melting of the α phase of iPP is examined by combined differential scanning calorimetry (DSC) and optical microscopy: calorimetric results are directly correlated with corresponding morphologies of microtome sections of DSC samples. On partial melting at various temperatures (hereafter referred to as T s ) located in a narrow range (4°C) below and near T m , the number of nuclei increases (as in classical self‐nucleation experiments), by several orders of magnitude; on subsequent cooling, the crystallization peak is shifted by up to 25°C. After partial melting in the lower part of the T s range and recrystallization, the polymers display a prominent morphology “memory effect” whereby a phantom pattern of the initial spherulite morphology is maintained. After partial melting in the upper part of the T s range the initial morphology is erased and self‐nucleation affects only the total number of nuclei. The present experimental procedures make it possible to define, under “standard” conditions, the crystallization range of the polymer and in particular, the maximum crystallization temperature achievable when “ideally” nucleated. © John Wiley &amp; Sons, Inc.

The relationship between the critical micellization concentration (cmc) of a surfactant in solution and its free energy of micellization is probably the most widely used one in surfactant science. Until recently, most surfactants discussed in the literature were made up of one polar head group, nonionic or ionic, bonded to a single hydrophobic moiety. Recently, studies have been initiated on new types of ionic surfactants: bolaforms, surfactants with divalent counterions, gemini, or dimeric surfactants, etc. This paper first derives the relationship between the cmc and for a very general type of ionic surfactant, made up of a surfactant ion containing i polar groups of valency zs bonded to j alkyl chains, with counterions of valency zc. The form of this relationship is examined for several types of ionic surfactants. It is shown that many reported studies did not use the correct relationship to evaluate the free energy of micellization from the value of the cmc. In particular, the counterion contribution was often neglected, which resulted in large errors. The use of the correct equations is shown to yield values for the free energy of transfer of a methylene group from water to the micellar pseudophase which are largely independent of the surfactant chemical structure, as it is to be expected.

The buildup of the first layers of a polystyrenesulfonate (PSS)/polyallylamine (PAH) multilayer is studied in situ by means of streaming potential measurements (SPM) and by scanning angle reflectometry (SAR). The results are discussed in the framework of a schematic representation of the multilayer in three zones: a precursor zone (I), a core zone (II), and an outer zone (III). This view seems to be supported by our experimental findings. The ζ potential of the multilayer determined by the SPM shows a symmetrical and constant charge inversion during the multilayer buildup. This seems to indicate an exact charge compensation in zone II and an excess charge that is entirely located in the outer zone III. It is also shown by SAR that a regular buildup regime, in which the thickness increment per layer is constant, is reached after the deposition of the first six polyelectrolyte layers, which gives an indication of the extension of zone I. The influence of the salt concentration CNaCl present in the polyelectrolyte solutions during multilayer buildup is also investigated. It is found that an increase of the salt concentration in the polyelectrolyte solutions leads to larger amounts of deposited polyelectrolytes and to thicker multilayers. The amount deposited per polyelectrolyte layer δQ (PSS or PAH) is correctly predicted by the law δQ = a· + b where α lies between 0.05 and 0.15. In addition, when a multilayer built up in salty solutions is brought in contact with pure water, it expands, indicating that the rinsing step mainly affects zone III of the multilayer, which appears thus to behave like a polyion layer. The structural changes of the multilayer consecutive to the replacement of the salt solution by pure water occur with characteristic times ranging from a few tens of minutes to several hours depending on the initial salt concentration. Finally, it is also found that the structural modifications of the film are fully reversible so that the initial multilayer structure is recovered when water is replaced again by the initial salt solution.

A novel two-dimensional system of colloidal particles with absolutely calibrated magnetic interaction is used to investigate static and dynamic properties at the 2D crystal to liquid phase transition. We observe two successive transitions from the solid to the liquid phase with an intermediate hexatic phase, in perfect agreement with the theory of Kosterlitz and Thouless. The absolute values of the transition temperatures are given, and we demonstrate that they depend neither on the system size nor on the cooling rate.

Using neutron reflectometry we have resolvedto high resolutionthe internal structure of self-assembled polyelectrolyte multilayer films and have developed a detailed molecular picture of such systems by analyzing the data with a composition-space refinement technique. We show that such surface films consist of stratified structures in which polyanions and polycations of individual layers interdigitate one another intimately. Nevertheless, the deposition technique leads to results that are predictable, if well-defined and constant environmental conditions are maintained during the preparation. For alternating layers of poly(styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH), adsorbed onto atomically flat surfaces, a roughening of successively deposited layers leads to a progressively larger number of adsorption sites for consecutive generations of adsorbed polymer, and thus to an increase in layer thicknesses with an increasing number of deposited layers. Because of the interpenetration of adjacent polyelectrolyte species, however, this increase settles quickly into an equilibrium thickness. In fully hydrated films (100% relative humidity), water occupies ≥40% of the volume within the films. About twice as much water (by volume) is associated with PSS as with PAH. Incorporated inorganic salt plays a minor role only, if any. The equilibrium thickness of the deposited layer structure may be fine-tuned via the ionic strength, I, of the solutions used for the preparation. We show that the dependence of the thickness dlp per layer pair on I is linear, with a sensitivity, Δdlp/ΔI = 16 Å × L/mol. Concurrently with the layer thickness the interface roughness σ between adjacent layers increases: σ ∼ 0.4 × dlp. In contrast to the ionic strength of the deposition solutions, the degree of polymerization of the polyanions used in the preparation plays a minor role only in determining the overall structure of the deposited films. The results reported here are quantitatively consistent with those of a recent study (Tarabia et al. J. Appl. Phys. 1998, 83, 725−732), if one assumes that the hydration of the polyelectrolyte molecules in the sample films investigated in the two studies is similar.

Multilayer superlattices incorporating colloidal metal nanoparticles have been synthesized by an approach based on self‐assembly. Teh method of synthesis is described and the results are presented from X‐ray reflectivity measurements, optical spectroscopy, and various microscopies, showing that they provide a consistent picture of the structure of the resulting multilayer superlattices (see Figure). fig. magnified image

We report here on the structural characterization of polyelectrolytes multilayer films formed by poly(l-glutamic acid) and poly(l-lysine) (PGA/PLL). The growth of this system is compared to that of poly(styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers by means of in situ atomic force microscopy (AFM) and by optical waveguide lightmode spectroscopy (OWLS). In contrary to the (PSS/PAH)i films that are growing linearly with the number of deposited layer pairs i, optical data evidenced that the (PGA/PLL)i films are characterized by an exponential growth. The analysis of the structure of the (PSS/PAH)i films reveals a smooth featureless surface covered by small globules. On the other hand, (PGA/PLL)i films form extended structures that appear with a vermiculate pattern. We propose a new growth mechanism based on polyelectrolyte diffusion in and out of the film coupled to the formation of polyanion/polycation complexes at the surface of the film in order to explain the whole results.

The self-diffusion coefficient of a series of DNA fragments ranging from 280 to 5386 bases has been measured by fluorescence recovery after photobleaching after thermal denaturation in 8 M urea. The total persistence length p of single-stranded DNAs and its variation in ionic strength down to 10-3 M has been deduced. The importance of the value of p versus the pore size a and contour length L of the DNA in the optimization of sequencing by gel electrophoresis is emphasized.

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTChemistry, Physical Chemistry, and Uses of Molecular Fluorocarbon−Hydrocarbon Diblocks, Triblocks, and Related Compounds—Unique "Apolar" Components for Self-Assembled Colloid and Interface EngineeringMarie Pierre Krafft*† and Jean G. Riess*‡View Author Information Université de Strasbourg, Institut Charles Sadron (SOFFT-CNRS), 23 rue du Loess, 67034 Cedex, Strasbourg, France, and Harangoutte-les-Roses, 68160 Ste-Croix-aux-Mines, France* Correspondence: [email protected] and [email protected]†Université de Strasbourg.‡Harangoutte-les-Roses.Cite this: Chem. Rev. 2009, 109, 5, 1714–1792Publication Date (Web):March 18, 2009Publication History Received12 July 2005Published online18 March 2009Published inissue 13 May 2009https://pubs.acs.org/doi/10.1021/cr800260khttps://doi.org/10.1021/cr800260kreview-articleACS PublicationsCopyright © 2009 American Chemical SocietyRequest reuse permissionsArticle Views7488Altmetric-Citations420LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Emulsions,Liquids,Molecules,Monolayers,Phase transitions Get e-Alerts

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Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

Polyelectrolyte film fabrication by successive spraying of polycation and polyanion solutions is described and compared to classic dipping. The poly(styrenesulfonate)/poly(allylamine) system is examined in detail. The influence of various parameters such as spraying time, polyelectrolyte concentration, and effect of film drying during multilayer construction is investigated. It is found that film deposition by spraying is easily controlled and very reliable. The thickness of the multilayers grows linearly with the number of deposition cycles similarly to what is observed when dipping substrates or when polyelectrolyte solutions flow over a surface. The assembly of films is very fast and leads to films with small surface roughness as estimated by atomic force microscopy and X-ray reflectometry. Spray deposition allows achieving regular multilayer growth even under conditions for which dipping fails to produce homogeneous films (e.g., extremely short contact times). Moreover, because drainage constantly removes a certain quantity of the excess material arriving at the surface, one can even skip the rinsing step and, thus, speed up even further the whole buildup process.

Abstract Suspensions of rod-like cellulose crystallites of axial ratio ≈ 20–40, prepared by acid hydrolysis of natural cellulose fibres with sulphuric acid, give stable ordered fluids that display well-formed textures and disclinations characteristic of chiral nematic liquid crystalline phases. The critical volume fraction for phase separation of salt-free suspensions is typically 0.03, with a relatively narrow biphasic region. Because of the negative diamagnetic susceptibility of cellulose, the ordered phase becomes oriented in a magnetic field with its chiral nematic axis parallel to the applied field.

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