Virginie Ponsinet
University of Bordeaux
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Virginie Ponsinet.
ACS Nano | 2013
Julie Angly; Antonio Iazzolino; Jean-Baptiste Salmon; Jacques Leng; Sivasankaran Prathap Chandran; Virginie Ponsinet; Anthony Désert; Aurélie Le Beulze; Stéphane Mornet; Miguel A. Correa-Duarte
We use evaporation within a microfluidic device to extract the solvent of a (possibly very dilute) dispersion of nanoparticles and concentrate the dispersion until a solid made of densely packed nanoparticles grows and totally invades the microfluidic geometry. The growth process can be rationalized as an interplay between evaporation-induced flow and kinetic and thermodynamic coefficients which are system-dependent; this yields limitations to the growth process illustrated here on two main cases: evaporation- and transport-limited growth. Importantly, we also quantify how colloidal stability may hinder the growth and show that care must be taken as to the composition of the initial dispersion, especially regarding traces of ionic species that can destabilize the suspension upon concentration. We define a stability chart, which, when fulfilled, permits us to grow and shape-up solids, including superlattices and extended and thick arrays of nanoparticles made of unary and binary dispersions, composites, and heterojunctions between distinct types of nanoparticles. In all cases, the geometry of the final solid is imparted by that of the microfluidic device.
Journal of Physical Chemistry B | 2008
Denis Bendejacq; Virginie Ponsinet
We consider a symmetrical poly(styrene- stat-(acrylic acid))- block-poly(acrylic acid), i.e., PSAA- b-PAA, diblock copolymer, with a molar fraction phi AA = 0.42 of acrylic acid, in the more hydrophobic PSAA statistical first block. We investigate its structural behavior at constant concentration in water using small-angle neutron scattering (SANS) by varying (i) the ionization of its acrylic acid motives via the pH by adding NaOH and (ii) the ionic strength of the solution by increasing the NaCl salt concentration c S. We present the resulting morphological phase diagram {pH, c S}, in which we identified two different lamellar phases presenting a smectic long-range order at small-to-intermediate ionizations and a spherical phase with a liquid-like short-range order at larger ionization. In the low-ionization regime, the first lamellar phase comprises a water-free PSAA lamellar core surrounded by a dense poly(acrylic acid) brush swollen with water. Its mostly hydrophobic core still being glassy, this phase is unable to reorganize and is frozen in. A detailed analysis of the SANS data shows the osmotic nature of the polyelectrolyte brush, in which the Na+ counterions are confined so that local electroneutrality is satisfied. Above the pH at which the PSAA statistical block starts ionizing, the PSAA lamellar core melts. The second lamellar phase identified then comprises a PSAA core thinner than that of the frozen-in previous phase, implying a significant increase of the core/water interface and a decrease of the brush surface density. The transition from the first lamellar phase to the second one can be quantitatively shown to result from the balance between the two contributions: (i) the extra interfacial cost between the thinner core and water and (ii) the associated gain in entropy of mixing for the counterions confined inside the brush. At even higher ionization, the diblocks finally form spherical objects with a very small, pH-dependent aggregation number and reach an apparent onset of self-association. When the highest ionization investigated is reached, the cores of these final spherical core-shell objects are found to contain a significant amount of water. We thereby demonstrate that at constant concentration, pH, and ionic strength both trigger a transition from frozen to molten hydrophobic phases as well as unexpected morphological transitions.
Materials horizons | 2016
Sergio Gómez-Graña; A. Le Beulze; Stéphane Mornet; Etienne Duguet; E. Grana; E. Cloutet; G. Hadziioannou; Jacques Leng; Jean-Baptiste Salmon; V. G. Kravets; A. N. Grigorenko; N. A. Peyyety; Virginie Ponsinet; Philippe Richetti; A. Baron; D. Torrent; P. Barois
Raspberry-like magnetic nanoclusters are synthesized and subsequently self-assembled to form a bulk metamaterial exhibiting strong isotropic optical magnetism in visible light. The magnetic response of the nanoclusters (metamolecules) and of the final assembled material are measured by independent optical experiments. The validity of the effective permeability parameter is probed by spectroscopic ellipsometry at variable incidence. Numerical simulations confirm the measurements.
Soft Matter | 2014
C. L. Folcia; J. Ortega; J. Etxebarria; S. Rodríguez-Conde; G. Sanz-Enguita; K. Geese; Carsten Tschierske; Virginie Ponsinet; P. Barois; Ron Pindak; LiDong Pan; Z. Q. Liu; B. K. McCoy; C. C. Huang
The polarity and structure of the phases of a liquid crystal constituted by thiophene-based bent-core molecules is investigated by means of optical second-harmonic generation (SHG), and resonant and conventional X-ray diffraction. The material studied is representative of a wide family of mesogens that contain silyl groups at the ends of the chains. These bulky terminal groups have been reported to give rise to smectic phases showing ferroelectric switching. However, the analysis of the SHG signal before and after application of electric fields has allowed us to establish unambiguously that the reported ferroelectricity is not intrinsic to the material but stabilized by the cell substrates once an electric field has been applied. In addition, the results obtained from resonant X-ray diffraction indicate that virgin samples have antiferroelectric undulated synclinic smectic structures.
Langmuir | 2012
Hélène Fay; Steven Meeker; Juliette Cayer-Barrioz; Denis Mazuyer; Isabelle Ly; Frédéric Nallet; Bernard Desbat; Jean-Paul Douliez; Virginie Ponsinet; Olivier Mondain-Monval
We study the phase behavior in water of a mixture of natural long chain fatty acids (FAM) in association with ethylenediamine (EDA) and report a rich polymorphism depending on the composition. At a fixed EDA/FAM molar ratio, we observe upon dilution a succession of organized phases going from a lamellar phase to a hexagonal phase and, finally, to cylindrical micelles. The phase structure is established using polarizing microscopy, SAXS, and SANS. Interestingly, in the lamellar phase domain, we observe the presence of defects upon dilution, which SAXS shows to correspond to intrabilayer correlations. NMR and FF-TEM techniques suggest that these defects are related to an increase in the spontaneous curvature of the molecule monolayers in the lamellae. ATR-FTIR spectroscopy was also used to investigate the degree of ionization within these assemblies. The successive morphological transitions are discussed with regards to possible molecular mechanisms, in which the interaction between the acid surfactant and the amine counterion plays the leading role.
ACS Nano | 2017
Jiaji Cheng; Guillaume Le Saux; Jie Gao; Thierry Buffeteau; Yann Battie; P. Barois; Virginie Ponsinet; Marie-Hélène Delville; Ovidiu Ersen; Emilie Pouget; Reiko Oda
Plasmonic nanoparticles, particularly gold nanoparticles (GNPs) hold a great potential as structural and functional building blocks for three-dimensional (3D) nanoarchitectures with specific optical applications. However, a rational control of their assembly into nanoscale superstructures with defined positioning and overall arrangement still remains challenging. Herein, we propose a solution to this challenge by using as building blocks: (1) nanometric silica helices with tunable handedness and sizes as a matrix and (2) GNPs with diameter varying from 4 to 10 nm to prepare a collection of helical GNPs superstructures (called Goldhelices hereafter). These nanomaterials exhibit well-defined arrangement of GNPs following the helicity of the silica template. Strong chiroptical activity is evidenced by circular dichroism (CD) spectroscopy at the wavelength of the surface plasmon resonance (SPR) of the GNPs with a anisotropy factor (g-factor) of the order of 1 × 10-4, i.e., 10-fold larger than what is typically reported in the literature. Such CD signals were simulated using a coupled dipole method which fit very well the experimental data. The measured signals are 1-2 orders of magnitude lower than the simulated signals, which is explained by the disordered GNPs grafting, the polydispersity of the GNPs, and the dimension of the nanohelices. These Goldhelices based on inorganic templates are much more robust than previously reported organic-based chiroptical nanostructures, making them good candidates for complex hierarchical organization, providing a promising approach for light management and benefits in applications such as circular polarizers, chiral metamaterials, or chiral sensing in the visible range.
Composites Part A-applied Science and Manufacturing | 1999
Dara L. Woerdeman; Nicolas Amouroux; Virginie Ponsinet; Gilles Jandeau; H. Hervet; Liliane Léger
The adhesion between an industrial-grade epoxy elastomer and a silanated glass surface was studied using the JKR (Johnson, Kendall and Roberts) technique. Both short-term and longer-term interactions were monitored between the two components. Different silane coupling agents and coating procedures are applied to the glass surfaces, and their effects on the adhesion measurements are investigated. The topography of the silanated surfaces was studied using atomic force microscopy, and correlations were made with the JKR adhesion data. An extensive error analysis was also conducted in an attempt to extract the deterministic content of the data from experimental scatter.
EPL | 1995
Virginie Ponsinet; P. Fabre; M. Veyssié
Lamellar phases doped with magnetic particles, called ferrosmectic phases, undergo a reorientation transition when submitted to a very weak magnetic field. In contrast to the predictions for thermotropic smectic phases, the development of that instability occurs through the appearance of localized defects. The critical field corresponding to that transition is calculated and compared to our experimental results. We discuss the occurrence of defect formation, rather than the expected homogeneous instability, in the more general terms of a second-order phase transition changed into first order by the presence of host particles.
Chemcatchem | 2015
Hui Shi; Zhaoyu Fan; Virginie Ponsinet; Remi Sellier; Honglai Liu; Marc Pera-Titus; Jean-Marc Clacens
Polystyrene‐grafted silica nanoparticles bearing sulfonic acid centers and with tunable amphiphilic properties were designed to perform the biphasic etherification reaction of glycerol with dodecanol at the interface of Pickering emulsions. By optimizing the hydrophobic properties of the particles, double Pickering emulsions could be generated allowing a facilitated diffusion of glycerol and dodecanol into the microenvironment near the acid centers.
Soft Matter | 2012
Benoît Maxit; Denis Bendejacq; Virginie Ponsinet
Robust water-swollen lamellar phases of an amphiphilic diblock copolymer were used to organize 7 nm large cerium oxide nanoparticles (NPs) from aqueous dispersions into well-ordered nanocomposites. The pH of the mixture controls the amount of nanocrystals successfully incorporated, found as high as 12 vol% of the total composite sample.