Virginie Ponsinet - Academia.edu (original) (raw)
Papers by Virginie Ponsinet
Bulletin of the American Physical Society, 2020
Nano Today, 2020
Self-assembly approaches, e.g. colloidal, emulsion and polymer phase separation, provide scientis... more Self-assembly approaches, e.g. colloidal, emulsion and polymer phase separation, provide scientists with an exotic yet direct platform to access technologically desired nanostructures at competitive costs. In particular, soft nanomaterial systems such as block copolymer (BCP) materials present a powerful means to tailor templates and spatially controlled systems that are amenable to large scale manufacturing practices. BCP nanoarchitectures in bulk, solution and thin film form can act as structural motifs to template foreign materials and pave the way towards important applications across industry and society. While extensive literature and research efforts exist on electronic device uses using BCPs, we look at nascent applications outside the integrated circuit realm. Recent reports are discussed including for example; lightharvesting (energy-section 2), metasurfaces (photonics-section 3), nanofiltration membranes (environmental-section 4) and antibacterial activity (biological-section 5). We endeavour to illustrate the window of opportunity presented through BCP self-assembly for nanomanufacturing. We believe the highlights discussed will aid in directing new research initiatives and facilitate the large-scale integration of BCP materials with broad societal impact.
Nanophotonics, 2018
The generation in artificial composites of a magnetic response to light, comparable in magnitude ... more The generation in artificial composites of a magnetic response to light, comparable in magnitude with the natural electric response, may offer an invaluable control parameter for a fine steering of light at the nanoscale. In many experimental realizations, however, the magnetic response of artificial meta-atoms is too weak so that there is a need for new designs with increased magnetic polarizability. Numerical simulations show that geometrical plasmonic nanostructures based on Platonic solids are excellent candidates for the production of strong optical magnetism in visible light. Inspired by these models, we report a bottom-up approach to synthesize plasmonic nanoclusters made of 12 gold patches located at the center of the faces of a dodecahedron. The scattering of the electric and magnetic dipole induced by light is measured across the whole visible range. The ratio of the magnetic to electric response at resonance is found three times higher than its counterpart measured on dis...
Nanoscale Advances, 2019
Block copolymer-templated gold nanostructured surfaces of high refractive index due to controlled... more Block copolymer-templated gold nanostructured surfaces of high refractive index due to controlled plasmonic nanoparticle shape.
Macromolecular rapid communications, Jan 16, 2018
Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route... more Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route to achieve well-defined metallic dot arrays, even if the variety of pattern symmetries is restricted due to the limited number of structures offered by microphase separated diblock copolymers. A strategy that relies on the use of complex network structures accessible through the self-assembly of linear ABC-type terpolymers is presented for the formation of metallic nanodots arrays with "outside-the-box" symmetries. Patterned templates formed by the cubic Q214 and orthorhombic O70 network structures are used as excellent platforms to build well-ordered gold nanodot arrays with unique p3m1 and p2 symmetries, respectively. A simple yet efficient blending strategy is used to tune the critical dimensions of the p3m1 pattern while laterally ordered gold nanodot arrays are also demonstrated through a directed self-assembly approach. Such highly ordered gold nanodots with tunable part...
EPL (Europhysics Letters), 2017
The concept of metamaterials emerged in years 2000 with the achievement of artificial structures ... more The concept of metamaterials emerged in years 2000 with the achievement of artificial structures enabling non conventional propagation of electromagnetic waves, such as negative phase velocity of negative refraction. The electromagnetic response of metamaterials is generally based on the presence of optically-resonant elementsor meta-atomsof sub-wavelength size and well designed morphology so as to provide the desired electric and magnetic optical properties. Top-down technologies based on lithography techniques have been intensively used to fabricate a variety of efficient electric and magnetic resonators operating from microwave to visible light frequencies. However, the technological limits of the top-down approach are reached in visible light where a huge number of nanometre sized elements is required. We show here that the bottom-up fabrication route based on the combination of nanochemistry and of the self-assembly methods of colloidal physics provide an excellent alternative for the large scale synthesis of complex meta-atoms, as well as for the fabrication of 2D and 3D samples exhibiting meta-properties in visible light.
ACS nano, Jan 25, 2017
Plasmonic nanoparticles, particularly gold nanoparticles (GNPs) hold a great potential as structu... more 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 lar...
Optics & Laser Technology, 2016
Abstract Self-assembled metamaterials constitute a promising platform to achieving bulk and homog... more Abstract Self-assembled metamaterials constitute a promising platform to achieving bulk and homogenous optical materials that exhibit unusual effective medium properties. For many years now, the research community has contemplated lithographically fabricated metasurfaces, with extraordinary optical features. However, achieving large volumes at low cost is still a challenge by top-down fabrication. Bottom-up fabrication, that relies both on nanochemistry and self-assembly, is capable of building such materials while greatly reducing the energy footprint in the formulation of the metamaterial. Self-assembled metamaterials have shown that they are capable of reaching unprecedented values of bulkiness and homogeneity figures of merit. This feat is achieved by synthesizing plasmonic nanoresonators (meta-atoms in the sense of artificial polarizable units) and assembling them into a fully three-dimensional matrix through a variety of methods. Furthermore it has been shown that a wide range of material parameters can be tailored by controlling the geometry and composition of the meta-atoms as well as the volume fraction of the nano-objects in the metamaterial. Here we conduct a non-comprehensive review of some of the recent trends in self-assembled optical metamaterials and illustrate these trends with our recent work.
Thin Solid Films, 2016
Disordered gold nanocomposite films were obtained by introducing spherical gold nanoparticles int... more Disordered gold nanocomposite films were obtained by introducing spherical gold nanoparticles into a polymer matrix. These films were structurally characterized using microscopy techniques, and then analyzed for their effective optical indices using spectroscopic ellipsometry. It is found that even for a low volume fraction of gold nanoparticles (f ∼ 1 − 5 %), the observed plasmonic resonance is affected by electromagnetic coupling between particles, related to the disorder of the particles. We show that the classical Maxwell Garnett Effective Medium Approximation (EMA) fails to predict the measured indices. Since couplings create deformations of the polarizability tensor of individual particles, we propose to take them into account phenomenologically using a modified Maxwell Garnett EMA based on a distribution of ellipsoidal polarizabilities. This modified model, albeit simple, appears appropriate: in simple cases, a unimodal distribution of ellipsoidal polarizabilities is used, allowing for good fits of the experimental data with only two free parameters. Bimodal distributions make it possible to handle more complex cases where the resonance presents a shoulder, suggesting that particles can then be categorized into weakly vs. strongly coupled resonators. Such modified Maxwell Garnett EMAs present the advantage of relying on physically meaningful parameters and could be a general tool for the phenomenological description of plasmonic couplings in different disordered nanocomposites.
The Journal of Physical Chemistry, 1996
We have measured the flexibility κ of the membranes of a quaternary lamellar phase of periodicity... more We have measured the flexibility κ of the membranes of a quaternary lamellar phase of periodicity d, without and with particles included between the layers. We show that an increase in cosurfactant amount in the membranes leads to a decrease of the flexibility constant κ, for the two studied systems. On the other hand, the membrane flexibility κ is shown to be hardly different in nondoped and doped (ferrosmectic) systems. This implies that the enhanced value of the elastic bending modulus K, observed when the lamellar phase is doped with particles, cannot be attributed to a simple hardening of the membranes. This leads us to question the well-known relationship between the elasticity of a lamellar phase and the elasticity of its constituting layers: K) κ/d, in the case of ferrosmectic phases.
Journal de Physique II, 1994
The Journal of Physical Chemistry, 1994
We describe in this paper the formation, structure, and magnetic properties of a new system which... more We describe in this paper the formation, structure, and magnetic properties of a new system which consists of a lyotropic hexagonal phase doped with colloidal magnetic particles. The initial nondoped lyotropic system is cyclohexane/SDS/water/pentanol, in which we replace the cyclohexane by a ferrofluid. The lattice parameter of these new phases is determined by small-angle X-ray scattering to be about 27 nm and thus significantly
Journal de Physique II, 1993
Applications of Metamaterials, 2009
Water-based lubricants are widely used in metal forming processes due to their good cooling and l... more Water-based lubricants are widely used in metal forming processes due to their good cooling and lubrication capabilities. In order to investigate the correlation between lubricant physico-chemical properties and tribological behaviour, this work focuses on simplified lubricants composed of ethylene diamine and fatty acids, dispersed in water. Herein, the phase behaviour of the system presents a succession of micellar, hexagonal and
Langmuir, 1999
We study the wetting properties by water of composite surfaces constructed from solid micrometer-... more We study the wetting properties by water of composite surfaces constructed from solid micrometer-size magnetic particles anchored at the interface of polymer films, in relation to the structure of the surface determined by atomic force microscopy and confocal microscopy. We measure the advancing and receding contact angles as functions of the anchoring position of the particles, and we show that the wetting hysteresis is caused mainly by the hydrophilicity of the magnetic particles. We show that the structure and the wettability of these surfaces can be strongly modified by the action of external magnetic field gradients. The effects of tangential gradients are dominant over normal ones and can be distinguished in two regimes according to their magnitude: the wetting hysteresis is controlled either by the hydrophilicity of the particles or by the induced roughness of the surface.
The Journal of Physical Chemistry B, 2008
We consider a symmetrical poly(styrene-stat-(acrylic acid))-block-poly(acrylic acid), i.e., PSAA-... more We consider a symmetrical poly(styrene-stat-(acrylic acid))-block-poly(acrylic acid), i.e., PSAA-b-PAA, diblock copolymer, with a molar fraction 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 liquidlike shortrange 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, pHdependent 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.
Physical Review E, 2011
The chiral antiferroelectric structure of an achiral bent-core liquid crystal is characterized fo... more The chiral antiferroelectric structure of an achiral bent-core liquid crystal is characterized for the first time by resonant x-ray scattering at chlorine K-edge. The "forbidden" reflections resulting from the glide or screw symmetry elements are restored by the anisotropy of the tensor structure factor which we calculate for two possible structural models. A careful analysis of the polarization states of the restored "forbidden" reflections enables an unambiguous identification of a chiral structure (i.e. the so-called anticlinic, antiferroelectric smectic-C or Sm-C A P A) co-existing with the achiral synclinic antiferroelectric smectic-C or Sm-C S P A. The method proves to be quite powerful as it identifies the chiral structure within coexisting phases despite an imperfect orientation of the sample. The volume fraction of the chiral phase and the distribution of alignment are extracted from the data.
Bulletin of the American Physical Society, 2020
Nano Today, 2020
Self-assembly approaches, e.g. colloidal, emulsion and polymer phase separation, provide scientis... more Self-assembly approaches, e.g. colloidal, emulsion and polymer phase separation, provide scientists with an exotic yet direct platform to access technologically desired nanostructures at competitive costs. In particular, soft nanomaterial systems such as block copolymer (BCP) materials present a powerful means to tailor templates and spatially controlled systems that are amenable to large scale manufacturing practices. BCP nanoarchitectures in bulk, solution and thin film form can act as structural motifs to template foreign materials and pave the way towards important applications across industry and society. While extensive literature and research efforts exist on electronic device uses using BCPs, we look at nascent applications outside the integrated circuit realm. Recent reports are discussed including for example; lightharvesting (energy-section 2), metasurfaces (photonics-section 3), nanofiltration membranes (environmental-section 4) and antibacterial activity (biological-section 5). We endeavour to illustrate the window of opportunity presented through BCP self-assembly for nanomanufacturing. We believe the highlights discussed will aid in directing new research initiatives and facilitate the large-scale integration of BCP materials with broad societal impact.
Nanophotonics, 2018
The generation in artificial composites of a magnetic response to light, comparable in magnitude ... more The generation in artificial composites of a magnetic response to light, comparable in magnitude with the natural electric response, may offer an invaluable control parameter for a fine steering of light at the nanoscale. In many experimental realizations, however, the magnetic response of artificial meta-atoms is too weak so that there is a need for new designs with increased magnetic polarizability. Numerical simulations show that geometrical plasmonic nanostructures based on Platonic solids are excellent candidates for the production of strong optical magnetism in visible light. Inspired by these models, we report a bottom-up approach to synthesize plasmonic nanoclusters made of 12 gold patches located at the center of the faces of a dodecahedron. The scattering of the electric and magnetic dipole induced by light is measured across the whole visible range. The ratio of the magnetic to electric response at resonance is found three times higher than its counterpart measured on dis...
Nanoscale Advances, 2019
Block copolymer-templated gold nanostructured surfaces of high refractive index due to controlled... more Block copolymer-templated gold nanostructured surfaces of high refractive index due to controlled plasmonic nanoparticle shape.
Macromolecular rapid communications, Jan 16, 2018
Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route... more Nanotemplates derived from the self-assembly of AB-type block copolymers provide an elegant route to achieve well-defined metallic dot arrays, even if the variety of pattern symmetries is restricted due to the limited number of structures offered by microphase separated diblock copolymers. A strategy that relies on the use of complex network structures accessible through the self-assembly of linear ABC-type terpolymers is presented for the formation of metallic nanodots arrays with "outside-the-box" symmetries. Patterned templates formed by the cubic Q214 and orthorhombic O70 network structures are used as excellent platforms to build well-ordered gold nanodot arrays with unique p3m1 and p2 symmetries, respectively. A simple yet efficient blending strategy is used to tune the critical dimensions of the p3m1 pattern while laterally ordered gold nanodot arrays are also demonstrated through a directed self-assembly approach. Such highly ordered gold nanodots with tunable part...
EPL (Europhysics Letters), 2017
The concept of metamaterials emerged in years 2000 with the achievement of artificial structures ... more The concept of metamaterials emerged in years 2000 with the achievement of artificial structures enabling non conventional propagation of electromagnetic waves, such as negative phase velocity of negative refraction. The electromagnetic response of metamaterials is generally based on the presence of optically-resonant elementsor meta-atomsof sub-wavelength size and well designed morphology so as to provide the desired electric and magnetic optical properties. Top-down technologies based on lithography techniques have been intensively used to fabricate a variety of efficient electric and magnetic resonators operating from microwave to visible light frequencies. However, the technological limits of the top-down approach are reached in visible light where a huge number of nanometre sized elements is required. We show here that the bottom-up fabrication route based on the combination of nanochemistry and of the self-assembly methods of colloidal physics provide an excellent alternative for the large scale synthesis of complex meta-atoms, as well as for the fabrication of 2D and 3D samples exhibiting meta-properties in visible light.
ACS nano, Jan 25, 2017
Plasmonic nanoparticles, particularly gold nanoparticles (GNPs) hold a great potential as structu... more 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 lar...
Optics & Laser Technology, 2016
Abstract Self-assembled metamaterials constitute a promising platform to achieving bulk and homog... more Abstract Self-assembled metamaterials constitute a promising platform to achieving bulk and homogenous optical materials that exhibit unusual effective medium properties. For many years now, the research community has contemplated lithographically fabricated metasurfaces, with extraordinary optical features. However, achieving large volumes at low cost is still a challenge by top-down fabrication. Bottom-up fabrication, that relies both on nanochemistry and self-assembly, is capable of building such materials while greatly reducing the energy footprint in the formulation of the metamaterial. Self-assembled metamaterials have shown that they are capable of reaching unprecedented values of bulkiness and homogeneity figures of merit. This feat is achieved by synthesizing plasmonic nanoresonators (meta-atoms in the sense of artificial polarizable units) and assembling them into a fully three-dimensional matrix through a variety of methods. Furthermore it has been shown that a wide range of material parameters can be tailored by controlling the geometry and composition of the meta-atoms as well as the volume fraction of the nano-objects in the metamaterial. Here we conduct a non-comprehensive review of some of the recent trends in self-assembled optical metamaterials and illustrate these trends with our recent work.
Thin Solid Films, 2016
Disordered gold nanocomposite films were obtained by introducing spherical gold nanoparticles int... more Disordered gold nanocomposite films were obtained by introducing spherical gold nanoparticles into a polymer matrix. These films were structurally characterized using microscopy techniques, and then analyzed for their effective optical indices using spectroscopic ellipsometry. It is found that even for a low volume fraction of gold nanoparticles (f ∼ 1 − 5 %), the observed plasmonic resonance is affected by electromagnetic coupling between particles, related to the disorder of the particles. We show that the classical Maxwell Garnett Effective Medium Approximation (EMA) fails to predict the measured indices. Since couplings create deformations of the polarizability tensor of individual particles, we propose to take them into account phenomenologically using a modified Maxwell Garnett EMA based on a distribution of ellipsoidal polarizabilities. This modified model, albeit simple, appears appropriate: in simple cases, a unimodal distribution of ellipsoidal polarizabilities is used, allowing for good fits of the experimental data with only two free parameters. Bimodal distributions make it possible to handle more complex cases where the resonance presents a shoulder, suggesting that particles can then be categorized into weakly vs. strongly coupled resonators. Such modified Maxwell Garnett EMAs present the advantage of relying on physically meaningful parameters and could be a general tool for the phenomenological description of plasmonic couplings in different disordered nanocomposites.
The Journal of Physical Chemistry, 1996
We have measured the flexibility κ of the membranes of a quaternary lamellar phase of periodicity... more We have measured the flexibility κ of the membranes of a quaternary lamellar phase of periodicity d, without and with particles included between the layers. We show that an increase in cosurfactant amount in the membranes leads to a decrease of the flexibility constant κ, for the two studied systems. On the other hand, the membrane flexibility κ is shown to be hardly different in nondoped and doped (ferrosmectic) systems. This implies that the enhanced value of the elastic bending modulus K, observed when the lamellar phase is doped with particles, cannot be attributed to a simple hardening of the membranes. This leads us to question the well-known relationship between the elasticity of a lamellar phase and the elasticity of its constituting layers: K) κ/d, in the case of ferrosmectic phases.
Journal de Physique II, 1994
The Journal of Physical Chemistry, 1994
We describe in this paper the formation, structure, and magnetic properties of a new system which... more We describe in this paper the formation, structure, and magnetic properties of a new system which consists of a lyotropic hexagonal phase doped with colloidal magnetic particles. The initial nondoped lyotropic system is cyclohexane/SDS/water/pentanol, in which we replace the cyclohexane by a ferrofluid. The lattice parameter of these new phases is determined by small-angle X-ray scattering to be about 27 nm and thus significantly
Journal de Physique II, 1993
Applications of Metamaterials, 2009
Water-based lubricants are widely used in metal forming processes due to their good cooling and l... more Water-based lubricants are widely used in metal forming processes due to their good cooling and lubrication capabilities. In order to investigate the correlation between lubricant physico-chemical properties and tribological behaviour, this work focuses on simplified lubricants composed of ethylene diamine and fatty acids, dispersed in water. Herein, the phase behaviour of the system presents a succession of micellar, hexagonal and
Langmuir, 1999
We study the wetting properties by water of composite surfaces constructed from solid micrometer-... more We study the wetting properties by water of composite surfaces constructed from solid micrometer-size magnetic particles anchored at the interface of polymer films, in relation to the structure of the surface determined by atomic force microscopy and confocal microscopy. We measure the advancing and receding contact angles as functions of the anchoring position of the particles, and we show that the wetting hysteresis is caused mainly by the hydrophilicity of the magnetic particles. We show that the structure and the wettability of these surfaces can be strongly modified by the action of external magnetic field gradients. The effects of tangential gradients are dominant over normal ones and can be distinguished in two regimes according to their magnitude: the wetting hysteresis is controlled either by the hydrophilicity of the particles or by the induced roughness of the surface.
The Journal of Physical Chemistry B, 2008
We consider a symmetrical poly(styrene-stat-(acrylic acid))-block-poly(acrylic acid), i.e., PSAA-... more We consider a symmetrical poly(styrene-stat-(acrylic acid))-block-poly(acrylic acid), i.e., PSAA-b-PAA, diblock copolymer, with a molar fraction 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 liquidlike shortrange 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, pHdependent 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.
Physical Review E, 2011
The chiral antiferroelectric structure of an achiral bent-core liquid crystal is characterized fo... more The chiral antiferroelectric structure of an achiral bent-core liquid crystal is characterized for the first time by resonant x-ray scattering at chlorine K-edge. The "forbidden" reflections resulting from the glide or screw symmetry elements are restored by the anisotropy of the tensor structure factor which we calculate for two possible structural models. A careful analysis of the polarization states of the restored "forbidden" reflections enables an unambiguous identification of a chiral structure (i.e. the so-called anticlinic, antiferroelectric smectic-C or Sm-C A P A) co-existing with the achiral synclinic antiferroelectric smectic-C or Sm-C S P A. The method proves to be quite powerful as it identifies the chiral structure within coexisting phases despite an imperfect orientation of the sample. The volume fraction of the chiral phase and the distribution of alignment are extracted from the data.