For glassy epoxy-amine thermosets with a large range of cross-link density and chemical composition, the surface energy was found to be minimum when the surface roughness measured with AFM is maximum for the highest cross-linked... more
For glassy epoxy-amine thermosets with a large range of cross-link density and chemical composition, the surface energy was found to be minimum when the surface roughness measured with AFM is maximum for the highest cross-linked materials. Indeed, at room temperature they are away from equilibrium and therefore have a lower density leading to a lower surface energy. In this study, the surface roughness is seen as a surface signature of the internal stress release which is maximum for the highest cross-linked network. A good agreement was observed between predicted and measured surface energy. Prediction was conducted considering the same composition at the surface and in the bulk. This result suggest that either selective adsorption is balanced by the chemical reaction which act as a strong negative interaction parameter or that bulk density is the main parameter which determines surface energy.
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Research Interests: Adsorption and Coacervate
In this paper, the effect of the main parameters which contributes to the adhesion between an epoxy-amine network and an amorphous high-Tg thermoplastic were studied. Micron-scale and molecular-level structures of the interface can be... more
In this paper, the effect of the main parameters which contributes to the adhesion between an epoxy-amine network and an amorphous high-Tg thermoplastic were studied. Micron-scale and molecular-level structures of the interface can be tailored from the knowledge of the phase diagram of the system, kinetics of epoxy-amine reaction, dissolution process, and possible grafting at the interface. A very high level of interfacial toughness between an epoxy-amine network and a thermoplastic can be achieved by selecting properly the chemistry of the involved components and the processing conditions. From such a study, a new methodology for improving polymer/polymer adhesion can be proposed.
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Research Interests: Chemical Engineering, Physics, Materials Science, Nanoparticle, Crystallization, and 15 moreNanotechnology, Medicine, Multidisciplinary, Cerium Oxide, Nanostructures, Colloids, Cerium, Particle Size, Molecular Conformation, Neutron Scattering, Adsorption Isotherm Models, Materials Testing, Polyethylene Glycols, Driving force, and Adsorption isotherm
Recent studies have pointed the importance of polyelectrolyte assembly in the elaboration of innovative nanomaterials. Beyond their structures, many important questions on the thermodynamics of association remain to be answered. Here, we... more
Recent studies have pointed the importance of polyelectrolyte assembly in the elaboration of innovative nanomaterials. Beyond their structures, many important questions on the thermodynamics of association remain to be answered. Here, we investigate the complexation between poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium acrylate) (PANa) chains using a combination of three techniques: isothermal titration calorimetry (ITC), static and dynamic light scattering and electrophoresis. Upon addition of PDADMAC to PANa or vice-versa, the results obtained by the different techniques agree well with each other, and reveal a two-step process. The primary process is the formation of highly charged polyelectrolyte complexes of sizes 100 nm. The secondary process is the transition towards a coacervate phase made of rich and poor polymer droplets. The binding isotherms measured are accounted for using a phenomenological model that provides the thermodynamic parameters for each re...
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Abstract- The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this... more
Abstract- The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this bacterium, while the genes of the second one have to be integrated by homologous recombination into the host genome. Transformation experiments were carried out with the three topological plasmid confor-mations, supercoiled, open circular and linear. Transformation through chromosomal inte-gration occurred at a higher frequency than transformation through plasmid replication. Moreover, this mechanism was less sensitive to differences in molecule conformation than was autonomous replication. These results suggest that genetic transformation proceeds more frequently via integration of DNA with sufficient sequence similarity into the host genome than by the autonomous replication of plasmid molecules. Key words: natural transformation, Acinetobacter sp., pla...
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Polymer chains in thin films are seen in a tremendous number of systems and devices of modern material science and technology. The need for controlled (thickness, Mw, conformations...), stable and reproducible thin films is then... more
Polymer chains in thin films are seen in a tremendous number of systems and devices of modern material science and technology. The need for controlled (thickness, Mw, conformations...), stable and reproducible thin films is then essential. We have developed an overall strategy to built-up chemisorbed thin films with tunable architectures grown directly from silica surface through controlled macromolecular chemistry [1]. The process is split in two distinct steps: (i) deposition of an initiator monolayer using "reactive" Langmuir-Blodgett deposition technique that allows the control of the chain lateral grafting density σ (up to 1.0 chain/nm2) (ii) the nitroxide mediated free radical polymerization of styrene
Engineered nanoparticles made from noble metals, rare-earth oxides or semiconductors are emerging as the central constituents of future nanotech developments. In this review, a survey of the complexing strategies between nanoparticles and... more
Engineered nanoparticles made from noble metals, rare-earth oxides or semiconductors are emerging as the central constituents of future nanotech developments. In this review, a survey of the complexing strategies between nanoparticles and oppositely charged polyelectrolytes developed during the last three years and based on electrostatic interactions is presented. These strategies include the one-step synthesis of stable and functionalized nanoparticles, the one- and multilayer coating of individual nano-objects, the controlled clustering of particles and the generation of capsules and thin films with superior functionalities. Among the formulation processes reported, three main classes are identified : the direct mixing route, the desalting transition pathway and the well-known layer by layer method. Finally, some latter developments, trends and applications of electrostatic assemblies in materials science and nanomedicine are highlighted.
Research Interests: Materials Science, Electrostatics, MRI, Nanoparticle, DNA, and 11 moreSEM, Thin Film, FORMULATION, NP, PEG, Particle, Ion, Layer by Layer, siRNA, Ions, and Polyelectrolyte
Polymer chains in thin films are seen in a tremendous number of systems and devices of modern material science and technology. The need for controlled (thickness, Mw, conformations...), stable and reproducible thin films is then... more
Polymer chains in thin films are seen in a tremendous number of systems and devices of modern material science and technology. The need for controlled (thickness, Mw, conformations...), stable and reproducible thin films is then essential. We have developed an overall strategy to built-up chemisorbed thin films with tunable architectures grown directly from silica surface through controlled macromolecular chemistry [1]. The process is split in two distinct steps : (i) deposition of an initiator monolayer using "reactive" Langmuir-Blodgett deposition technique that allows the control of the chain lateral grafting density σ (up to 1.0 chain/nm) (ii) the nitroxide mediated free radical polymerization of styrene that allows the control of chain length N. It induces a direct control of both brush thickness h and chain stretch S. The active chain ends enables to reinitiate the polymerization. We describe here neutron reflectivity measurements performed on the EROS reflectometer ...
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Thin layers of polystyrene were grown loosely or densely from silica surface via controlled living free radical polymerization. The reactive Langmuir-Blodgett deposition method allowed an effective control of the initiator layer density... more
Thin layers of polystyrene were grown loosely or densely from silica surface via controlled living free radical polymerization. The reactive Langmuir-Blodgett deposition method allowed an effective control of the initiator layer density leading to polystyrene brushes with different stretching of grafted chains. Consecutive polymerization runs performed on the same surface showed the living nature of the system and that the first run determine the final layer features. AFM imaging, wetting measurements and ellipsometry were used to characterize the layers. Preliminary experiments on surface mobility indicate an increase of Tg over dip coated layer. We also show data on AFM tip derivatized in the same way.
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We report on the generation of Smart hybrid functional surfaces via a novel surface functionalization pathway termed as Surface Grown Hybrid Functional Layers or SgL, which competes with the conventioanl Layer-by-Layer (LbL) approach. In... more
We report on the generation of Smart hybrid functional surfaces via a novel surface functionalization pathway termed as Surface Grown Hybrid Functional Layers or SgL, which competes with the conventioanl Layer-by-Layer (LbL) approach. In SgL approach, the smart surfaces were generated in a single step at a fluid/solid interface through fine tuning of electro-static interaction between the stable oppositely charged building blocks (BBs) as a function of the ionic strength of the dispersion. Admixing of the oppositely charged BBs at high ionic strength resulted a dormant solution, where the elctrostatic interaction is completely switched off. The complexation between the BBs can be triggered by switching back on the interaction via a controlled removal of salt (desalting) by dialysis or dilution with water yield a reactive solution. The onset of this desalting transition at a given substrate enabled the fabrication of smart hybrid layers with unique morphology, properties and applicat...
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The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this bacterium, while... more
The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this bacterium, while the genes of the second one have to be integrated by homologous recombination into the host genome. Transformation experiments were carried out with the three topological plasmid conformations, supercoiled, open circular and linear. Transformation through chromosomal integration occurred at a higher frequency than transformation through plasmid replication. Moreover, this mechanism was less sensitive to differences in molecule conformation than was autonomous replication. These results suggest that genetic transformation proceeds more frequently via integration of DNA with sufficient sequence similarity into the host genome than by the autonomous replication of plasmid molecules.
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Le systeme modele choisi montre la potentialite de l'association de la polymerisation radicalaire controlee et du greffage par Langmuir-Blodgett vis a vis de la formation de brosses de polystyrene sur support de silice. L'etude... more
Le systeme modele choisi montre la potentialite de l'association de la polymerisation radicalaire controlee et du greffage par Langmuir-Blodgett vis a vis de la formation de brosses de polystyrene sur support de silice. L'etude d'un certain nombre de parametres comme la densite en amorceurs ou la longueur des chaines greffees permet d'identifier les mecanismes specifiques de la polymerisation en surface et de mettre en evidence l'influence de l'organisation de la couche greffee sur la mobilite des chaines.
The surface layer of polymers exhibits different composition, morphol ogy and structure, also in the nanoscale, from the bulk material. The paper demonstrates the clearest examples, discussing consequences of the gradient nature of the... more
The surface layer of polymers exhibits different composition, morphol ogy and structure, also in the nanoscale, from the bulk material. The paper demonstrates the clearest examples, discussing consequences of the gradient nature of the materials from the aspect of their exploitation (mainly hardness profile and friction). The ability of low molecular weight substances to migrate in a polymer matrix and the surface segregation occurring in polymer blends, are studied by FTIR, AFM, XPS, microindentation, microfriction, contact angle and DSC techni ques. It has been proved that the surface layer of polymer materials can be shaped during both compounding and process ing.
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... Figure 3 A) Schematic view of silicium wafer or AFM tip functionalization using Self Assembled Monolayers (SAM) from silanes or thiols chemistry able to react ... Nous pouvons voir sur la figure 6a l'effet de la masse molaire... more
... Figure 3 A) Schematic view of silicium wafer or AFM tip functionalization using Self Assembled Monolayers (SAM) from silanes or thiols chemistry able to react ... Nous pouvons voir sur la figure 6a l'effet de la masse molaire (ou de l'épaisseur greffée) et de la nature du liquide ...
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The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this bacterium, while... more
The naturally competent proteobacterium Acinetobacter sp. strain BD413 was used to determine the capacities of two replicons to transfer genes via transformation. One of these plasmids could replicate autonomously in this bacterium, while the genes of the second one have to be integrated by homologous recombination into the host genome. Transformation experiments were carried out with the three topological plasmid
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Recent studies have pointed out the importance of polyelectrolyte assembly in the elaboration of innovative nanomaterials.
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ABSTRACT
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ABSTRACT
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ABSTRACT
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ABSTRACT Superhydrophobic surfaces correspond to hydrophobic surfaces whose water contact angle is higher than 150 degrees. Two new routes involving plasma technique are proposed to prepare such surfaces: the first one is a one-step... more
ABSTRACT Superhydrophobic surfaces correspond to hydrophobic surfaces whose water contact angle is higher than 150 degrees. Two new routes involving plasma technique are proposed to prepare such surfaces: the first one is a one-step process (CF(4) plasma modification of low density polyethylene), and the second involves two steps (O(2) plasma treatment followed by CF(4) plasma treatment). The plasma parameters are defined to optimize the degradation and/or the functionalization. The O(2) plasma allows to create a variable roughness while CF(4) plasma accentuates this roughness and creates a non-polar layer. With the two-step treatment, plasma parameters were found which produced superhydrophobic surfaces with a controlled roughness and whose chemical structure was close to a Teflon-like structure. The wetting and dewetting of these superhydrophobic surfaces are compared to those of only hydrophobic polyethylene. The behavior of surfaces, whether dry or prewetted with water vapor, is found to be different. The dewetting of the dried surface previously prewetted is found to be discontinuous, and slower than that of the dry one. This specific behavior is interpreted as a roughness effect on trapped water. However, its dewetting is still faster than that of the corresponding hydrophobic surface such as PTFE. (c) Koninklijke Brill NV, Leiden, 2009
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The synthesis of low density polyethylene (LDPE) ultrahydrophobic surfaces with controlled roughness and transparency was described in a two steps O{2} and CF{4} plasmas treatment. Water contact angle as high as 171°, contact angle... more
The synthesis of low density polyethylene (LDPE) ultrahydrophobic surfaces with controlled roughness and transparency was described in a two steps O{2} and CF{4} plasmas treatment. Water contact angle as high as 171°, contact angle hysteresis less than 4°, and sliding angle as 4° were obtained on those surfaces. The surfaces with small roughness reached 85% of transparency between 400 nm
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We report here the first successful growth of Polystyrene brushes directly from the apex of a conventional AFM tip using a Langmuir-Blodgett deposition technique associated with a controlled free radical polymerization. The efficiency of... more
We report here the first successful growth of Polystyrene brushes directly from the apex of a conventional AFM tip using a Langmuir-Blodgett deposition technique associated with a controlled free radical polymerization. The efficiency of the grafting together with the possibility to form multi-layers are checked through AFM force measurements between a bare or functionalized tip and a silicon wafer in water or xylene.
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ABSTRACT Soils contaminated by prions, the infectious agents responsible for transmissible spongiform encephalopathy diseases, remain infectious to grazing animals for many years. In this study, the ability of enzymes produced by soil... more
ABSTRACT Soils contaminated by prions, the infectious agents responsible for transmissible spongiform encephalopathy diseases, remain infectious to grazing animals for many years. In this study, the ability of enzymes produced by soil microbes to degrade a recombinant prion protein (recPrP) was investigated in a loamy soil. A 15N‐labelled recPrP was added to soil in which microbial biomass and soil proteolytic activity had been increased by either simultaneous or prior amendment with lamb brain, and distribution of 15N among soil solid particles, soluble molecules and bacterial biomass was determined. After 1 day the proportions of recovered recPrP‐N associated with microbial biomass and soluble molecules were 6–9 and 15–19%, respectively, which is consistent with the hypothesis of degradation. A greater incorporation of 15N‐derived β‐sheeted recPrP into the microbial biomass pool occurred when the soil proteolytic activity was pre‐stimulated by a lamb brain amendment, suggesting that the recPrP degradation in soil is mediated by the activity level of proteolytic enzymes produced by the microbial biomass. The majority (35–87%) of the recovered recPrP‐N was associated with the soil particles. An observed partial degradation of recPrP deposited on a mica surface by soil soluble enzymes indicated a sorption‐related resistance to proteolysis. In conclusion, integration of the stimulation and turnover of the soil microbial component, after an input of a large amount of animal organic matter with the sorption properties of prion protein, is required to model and predict prion survivability, transformation and transmissibility in soil.
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The interactions between unsaturated phospholipid bilayers deposited on mica were measured in aqueous solution using a surface forces apparatus. The bilayers were made of L-alpha-dioleoylphosphatidyl-choline (DOPC),... more
The interactions between unsaturated phospholipid bilayers deposited on mica were measured in aqueous solution using a surface forces apparatus. The bilayers were made of L-alpha-dioleoylphosphatidyl-choline (DOPC), L-alpha-dioleoylphosphatidyl ethanolamine (DOPE), and mixtures of the two, and were formed on mica by Langmuir-Blodgett deposition after the lipids were spread on an aqueous substrate from a chloroform solution. The forces are interpreted as electrostatic double-layer and van der Waals forces with long range, and a strong repulsion (hydration or steric force) at distances of several nm. Together they produce a region of weak attraction (a secondary minimum) at 5 nm (DOPE) and 6 nm (DOPE). Fusion of two bilayers into one was observed when the local force per unit area was 2-3 MPa. Other researchers report that phosphatidylethanolamine in vesicles enhances fusion. In this study using deposited bilayers, the presence of DOPE in a DOPC bilayer did not promote fusion, nor did DOPE bilayers fuse more easily than DOPC. The value of the force per unit area at which the two bilayers fuse into one was however decreased by several orders of magnitude when the bilayers were formed from lipids kept in chloroform solution for several days or more. Chromatography showed traces of lipid degradation products in such chloroform solutions.