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An in-situ visualisation of the microstructure of a Carbopol gel flowing in a micro-channel is presented. By means of a novel chemical protocol able to stain the solid material units of the gel with a fluorescent molecule we are able to accurately identify the solid/fluid material units advected by the confined microscopic flow. Based on this novel visualisation technique a full statistical description of the distributions of solid–fluid material units in the flow in terms of space and time averages, probability density functions and space–time correlations is reported for the first time.

International audience; In this study, microbial fuel cells (MFCs) - operated with novel cation- and anion-exchange membranes, in particular AN-VPA 60 (CEM) and PSEBS DABCO (AEM) - were assessed comparatively with Nafion proton exchange membrane (PEM). The process characterization involved versatile electrochemical (polarization, electrochemical impedance spectroscopy - EIS, cyclic voltammetry - CV) and biological (microbial structure analysis) methods in order to reveal the influence of membrane-type during start-up. In fact, the use of AEM led to 2-5 times higher energy yields than CEM and PEM and the lowest MFC internal resistance (148 +/- 17 Omega) by the end of start-up. Regardless of the membrane-type, Geobacter was dominantly enriched on all anodes. Besides, CV and EIS measurements implied higher anode surface coverage of redox compounds for MFCs and lower membrane resistance with AEM, respectively. As a result, AEM based on PSEBS DABCO could be found as a promising material to substitute Nafion.

Contains fulltext : 232076.pdf (Publisher’s version ) (Open Access) Tumor-specific neoantigens can be highly immunogenic, but their identification for each patient and the production of personalized cancer vaccines can be time-consuming and prohibitively expensive. In contrast, tumor-associated antigens are widely expressed and suitable as an off the shelf immunotherapy. Here, we developed a PLGA-based nanoparticle vaccine that contains both the immunogenic cancer germline antigen NY-ESO-1 and an α-GalCer analog IMM60, as a novel iNKT cell agonist and dendritic cell transactivator. Three peptide sequences (85-111, 117-143, and 157-165) derived from immunodominant regions of NY-ESO-1 were selected. These peptides have a wide HLA coverage and were efficiently processed and presented by dendritic cells via various HLA subtypes. Co-delivery of IMM60 enhanced CD4 and CD8 T cell responses and antibody levels against NY-ESO-1 in vivo. Moreover, the nanoparticles have negligible systemic toxicity in high doses, and they could be produced according to GMP guidelines. Together, we demonstrated the feasibility of producing a PLGA-based nanovaccine containing immunogenic peptides and an iNKT cell agonist, that is activating DCs to induce antigen-specific T cell responses.

The question of whether Carbopol gels always behave as “model” yield stress material is addressed experimentally. Prompted by several simple hydrodynamic experiments performed with Carbopol gels that can not be fully understood within the commonly accepted “model” picture, we revisit the yielding behaviour of a Carbopol gel. When subjected to a loading/unloading process, the yielding of the Carbopol is gradual and exhibits a rheological hysteresis. By in-situ visualisation of the microstructure it is demonstrated that these features do not originate from a micro-structural damage of the micro-gel. A systematic description of the role of the rate at which the material is forced (loaded or unloaded) on the yielding scenario is given. In closing, the question of how simple a scalar model can be and yet accurately describe the experimentally observed yielding scenario of a Carbopol gel in a rheometric flow is addressed. It is concluded that simple scalar models may do such job as long as they are not too simple and include a minimal amount of physical ingredients.

International audience; The development of flexible drug delivery systems that can be tuned as a function of the drug to bedelivered and of the target disease is crucial in modern medicine. For this aim, novel amphiphilic poly-(e-caprolactone)-g-poly(ethylene glycol) (PCL-g-PEG) copolymers with well-controlled design weresynthesized by thiol–yne photochemistry. The grafting density and the copolymer amphiphilicity wereeasily controlled via the reaction parameters: concentration, reaction time, PEG length and the molarratio between PCL and PEG or the photoinitiator in the reaction mixture. The self-assembling behaviorof the copolymers was studied and a correlation between the composition of PCL-g-PEG and thenanoaggregate diameter sizes (28 to 73 nm) and critical aggregation concentrations (1.1 to 4.3 mg L1)was found. The influence of copolymer amphiphilicity on the drug loading was evaluated with variousdrugs including anticancer drugs (paclitaxel, ABT-199), drugs to overcome multidrug resistance incancer cells (curcumin, elacridar), an anti-inflammatory drug (dexamethasone) and an antibacterial drug(clofazimine). Finally, the influence of amphiphilicity on curcumin release and toxicity towards MCF-7cancer cell lines was studied. The impact of the grafting density, PEG length and the overall EG/CL ratiois discussed in detail. Curcumin loaded PCL-g-PEG with lower EG/CL ratios and shorter PEG chainsshowed higher toxicity compared to their more hydrophilic counterparts.

International audience; Persistent luminescence nanoparticles (PLNPs) are innovative nanomaterials highly useful for bioimaging applications. Indeed, due to their particular optical properties, i.e., the ability to store the excitation energy before slowly releasing it for a prolonged period of time, they allow in vivo imaging without auto-fluorescence and with a high target to background ratio. However, as for most nanoparticles (NPs), without any special surface coating, they are rapidly opsonized and captured by the liver after systemic injection into small animals. To overcome this issue and prolong nanoparticle circulation in the bloodstream, a new stealth strategy was developed by covering their surface with poly(N-2-hydroxypropyl)methacrylamide (pHPMA), a highly hydrophilic polymer widely used in nanomedicine. Preliminary in vivo imaging results demonstrated the possibility of pHPMA as an alternative strategy to cover ZnGa 2 O 4 :Cr NPs to delay their capture by the liver, thereby providing a new perspective for the formulation of stealth NPs.

International audience; Submicronic molecularly imprinted polymer (MIP) colloids were synthesized by polymerization in aqueous dispersed media for selective separation of nonylphenol (NP) organic pollutant. A miniemulsion polymerization process based on ultrasheared monomer droplets has allowed for dispersion of the hydrophobic organic pollutant template to produce water-dispersible colloidal MIP. Structural parameters of the cross-linked polymer particles were tuned during the synthesis to achieve the best compromise between good specificity of imprinted polymer (MIP) sorbent compared to nonimprinted polymer (NIP) (i.e., imprinting factor (α)), sufficient level of adsorption capacity (Q), and selectivity of MIP toward the organic pollutant. For that purpose, the polymerization takes place in the organic monomer droplets containing nonylphenol (NP), N-vinylcaprolactam (VCL), different comonomers (vinyl acetate (VAc), vinyl benzoate (VB), or 2-ethylhexanoic acid vinyl ester (VeoVa-EH)), and various contents of divinyl adipate (DVA) cross-linker. Tuning the level of hydrophobic interactions, either by the hydrophobicity of the comonomer (VeoVa-EH > VB > VAc) or by the polarity of the hydroalcoholic mixture used for interfacial adsorption, achieved imprinting factors above unity. The binding of NP follows a monolayer Langmuir adsorption, and the present MIPs selectively recognize NP compared to phenol. Isothermal titration calorimetry (ITC) measurements corroborated both specificity (ΔHMIP > ΔHNIP) and selectivity with very low values of binding enthalpy for phenol, p-cresol, and 1-octanol compared to that of NP.

Among the biopolymers from animal sources, keratin is one the most abundant, with a major contribution from side stream products from cattle, ovine and poultry industry, offering many opportunities to produce cost-effective and sustainable advanced materials. Although many reviews have discussed the application of keratin in polymer-based biomaterials, little attention has been paid to its potential in association with other polymer matrices. Thus, herein, we present an extensive literature review summarizing keratin’s compatibility with other synthetic, biosynthetic and natural polymers, and its effect on the materials’ final properties in a myriad of applications. First, we revise the historical context of keratin use, describe its structure, chemical toolset and methods of extraction, overview and differentiate keratins obtained from different sources, highlight the main areas where keratin associations have been applied, and describe the possibilities offered by its chemical toolset. Finally, we contextualize keratin’s potential for addressing current issues in materials sciences, focusing on the effect of keratin when associated to other polymers’ matrices from biomedical to engineering applications, and beyond.

The development of nanomedicines for the treatment of neurodegenerative disorders demands innovative nanoarchitectures for combined loading of multiple neuroprotective compounds. We report dual-drug loaded monoolein-based liquid crystalline architectures designed for the encapsulation of a therapeutic protein and a small molecule antioxidant. Catalase (CAT) is chosen as a metalloprotein, which provides enzymatic defense against oxidative stress caused by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). Curcumin (CU), solubilized in fish oil, is co-encapsulated as a chosen drug with multiple therapeutic activities, which may favor neuro-regeneration. The prepared self-assembled biomolecular nanoarchitectures are characterized by biological synchrotron small-angle X-ray scattering (BioSAXS) at multiple compositions of the lipid/co-lipid/water phase diagram. Constant fractions of curcumin (an antioxidant) and a PEGylated agent (TPEG1000) are included with regard to the lipid fraction. Stable cubosome architectures are obtained for several ratios of the lipid ingredients monoolein (MO) and fish oil (FO). The impact of catalase on the structural organization of the cubosome nanocarriers is revealed by the variations of the cubic lattice parameters deduced by BioSAXS. The outcome of the cellular uptake of the dual drug-loaded nanocarriers is assessed by performing a bioassay of catalase peroxidatic activity in lysates of nanoparticle-treated differentiated SH-SY5Y human cells. The obtained results reveal the neuroprotective potential of the in vitro studied cubosomes in terms of enhanced peroxidatic activity of the catalase enzyme, which enables the inhibition of H2O2 accumulation in degenerating neuronal cells.

International audience; Stereolithography‐assisted fabrication of hydrogels of carboxybetaine methacrylamide (CBMAA) and a α,ω‐methacrylate poly(d,l‐lactide‐block‐ethylene glycol‐block‐ d,l‐lactide) (MA‐PDLLA‐PEG‐PDLLA‐MA) telechelic triblock macromer is presented. This technique allows printing complex structures with gyroid interconnected porosity possessing extremely high specific area.Hydrogels are characterized by infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and laser scanning confocal microscopy (LSCM). The copolymerization with zwitterionic comonomer leads hydrogels with high equilibrium water content (EWC), up to 700% while maintaining mechanical robustness. The introduction of carboxybetaine yields excellent resistance to nonspecific protein adsorption while providing a facile way for specific biofunctionalization with a model protein, fluorescein isothiocyanate labeled bovine serum albumin (BSA). The homogeneous protein immobilization across the hydrogel pores prove the accessibility to the innermost pore volumes.The remarkably low protein adsorption combined with the interconnected nature of the porosity allowing fast diffusion of nutrient and waste product and the mimicry of bone trabecular, makes the hydrogels presented here highly attractive for tissue engineering.

International audience; Effective drug delivery is restricted by pathophysiological barriers in solid tumors. In human pancreatic adenocarcinoma, poorly-permeable blood vessels limit the intratumoral permeation and penetration of chemo or nanotherapeutic drugs. New and clinically viable strategies are urgently sought to breach the neoplastic barriers that prevent effective drug delivery. Here, we present an original idea to boost drug delivery by selectively knocking down the tumor vascular barrier in a human pancreatic cancer model. Clinical radiation activates the tumor endothelial-targeted gold nanoparticles to induce a physical vascular damage due to the high photoelectric interactions. Active modulation of these tumor neovessels lead to distinct changes in tumor vascular permeability. Noninvasive MRI and fluorescence studies, using a short-circulating nanocarrier with MR-sensitive gadolinium and a long-circulating nanocarrier with fluorescence-sensitive nearinfrared dye, demonstrate more than two-fold increase in nanodrug delivery, post tumor vascular modulation. Functional changes in altered tumor blood vessels and its downstream parameters, particularly, changes in Ktrans (permeability), Kep (flux rate), and Ve (extracellular interstitial volume), reflect changes that relate to augmented drug delivery. The proposed dual-targeted therapy effectively invades the tumor vascular barrier and improve nanodrug delivery in a human pancreatic tumor model and it may also be applied to other nonresectable, intransigent tumors that barely respond to standard drug therapies.

Many phytochemical antioxidant compounds, including curcumin (CU), are water-insoluble and thus require delivery carriers in order to increase their bioavailability for in vivo applications. Oxidative stress-related apoptosis is a common cause for the neuronal loss in the progression of neurodegenerative diseases. Lipid nanoparticles (NPs) with internal self-assembled liquid crystalline structures present strong interest as safe drug delivery systems for neuronal regeneration through combination therapies. Here, we report spongosome and cubosome lipid NPs, which co-encapsulate CU and fish oil (FO), rich in ω-3 polyunsaturated fatty acids. The performed structural investigation by synchrotron small-angle X-ray scattering evidenced the liquid crystalline organization of the self-assembled NPs. The encapsulation efficiency for CU in the lipid nanocarriers was found to be higher as compared to that reported for polymer-based carriers. The cytotoxicity of the blank and antioxidant-loaded nanocarriers was negligible at lipid concentrations 300 and 500 nM. Morphological changes were observed for neuronally derived human SH-SY5Y cells subjected to damage by reactive oxygen species (ROS) upon exposure to hydrogen peroxide. Using flow cytometry, we quantified the effects of CU and FO, co-encapsulated in spongosome and cubosome lipid NPs on the response of differentiated SH-SY5Y cells to $H_{2}O_{2}$-induced oxidative stress. Measurements of the intracellular ROS levels (using a 2′,7′-dichlorodihydrofluorescein diacetate probe) and of apoptotic cells (using an Annexin V-PE/SYTOX-green assay) were performed to compare the neuroprotective potential of the liquid crystalline spongosome and cubosome nanocarriers to that of ethanolic solutions or aqueous suspensions of the CU/FO mixtures. The results indicated that dual drug-loaded cubosomes may be suitable for combination treatments against neurodegenerative disorders.

International audience; Structural control over design and formation of selfassembled nanomaterials for neuroprotection and neuroregeneration is crucial for their application in nanomedicine. Here a synthetic construct of the pituitary adenylate cyclase-activating polypeptide (PACAP38) coupled to a docosahexaenoic acid (DHA: an ω-3 polyunsaturated fatty acid (PUFA)) is designed towards the creation of compartmentalized liquid crystalline assemblies of neuroprotective compounds. The hormone PACAP38 is a ligand of the class B PAC1 G-protein-coupled receptor (GPCR), whereas DHA is a lipid trophic factor. The lipidated peptide PACAP-DHA is co-assembled into hierarchical nanostructures elaborated from hybrid vesicle-micelle reservoirs as well into PEGylated cubosomes composed of multiple neuroprotective building blocks. The resulting nanostructures are determined by synchrotron small-angle X-ray scattering (BioSAXS) and cryogenic transmission electron microscopy (cryo-TEM). Multicompartment topologies are obtained in a twofold approach: (i) intriguing compartmentalized vesicles, which embed pep-lipid micelles forming nanopatterns, and (ii) multidomain pep-lipid cubosomes. Both kinds of topologies are favorable for sustainedrelease applications in combination therapies of neurodegeneration. The organizational complexity of the scaffolds involving the lipidated high-molecular weight peptide hormone is beyond the one that has been reached with small lipid-like peptide surfactants.

Journal of molecular liquids 279, 518 - 523 (2019). doi:10.1016/j.molliq.2019.01.124, We investigate the nanostructure evolution and the membrane reorganization of diluted lipid dispersions of self-assembled monoolein (MO)/eicosapentaenoic acid (EPA, 20:5) mixtures by synchrotron small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) microscopy. The nonlamellar lipid phase containing a ω-3 polyunsaturated fatty acid was fragmented into stable nanoscale objects with the help of PEGylated lipids. The Cryo-TEM imaging revealed the transformation pathway of the vesicular bilayer membranes into sponge nanoparticles (spongosomes) in excess aqueous medium. At ambient temperature, the topological transition occurred through the proliferation of membrane-linking pores (MLP) within the individual lipid nanoparticles. The density of the MLP pores varied starting from the nanoparticle center toward the periphery. The generation of MLP is governed by the amphiphilic composition and leads to formation of 3D networks of aqueous channels inside the nanoparticles, i.e. spongosomes. A higher density of MLP pores was established at increasing fraction of EPA in the mixed lipid membranes. This corresponded to sponge particles of less hydrated internal structure, i.e. with smaller-size aqueous compartments. Synchrotron SAXS patterns characterized the overall structural transition from vesicles to sponge membranes in the studied lipid systems. It can be concluded that the incorporation of a ω-3 polyunsaturated fatty acid at increasing concentration causes swelling inhibition (dehydration) of the host liquid crystalline architectures., Published by Elsevier, New York, NY [u.a.]

We developed a new simplified method for the synthesis of well-defined linear, diblock, or starlike N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer drug carriers using controlled reversible addition-fragmentation chain transfer polymerization. The prepared monodispersed polymers are after the drug attachment intended for enhanced anticancer therapy. This new approach significantly reduces the number of required synthetic steps and minimizes the consumption of organic solvents during the synthesis. As a result, highly defined linear, diblock, and starlike copolymers designed for pH-triggered drug activation/release in tumor tissue were formed in sufficient amounts for further physicochemical and biological studies. Within the synthesis, we also developed a new procedure for the selective deprotection of tert-butoxycarbonyl hydrazide and amine groups on hydrophilic HPMA copolymers, including the one-pot removal of polymer end groups. We studied and described in detail the kinetics and efficacy of the deprotection reaction. We believe the simplified synthetic approach facilitates the preparation of polymer conjugates bound by the pH-sensitive hydrazone bond and their application in tumor treatment.

International audience; ovel pH- and thermoresponsive amphiphilic diblock copolymer, comprising hydrophilic poly(2-dimethylaminoethyl acrylate) (PDMAEA) and amphiphilic poly(styrene-grad-2-dimethylaminoethyl acrylate) (P(S-grad-DMAEA)) blocks, was synthesized by nitroxide-mediated radical polymerization. A series of copolymers (PS-grad-PDMAEA) with controlled molar masses and low dispersities over a wide range of monomer feed ratios (0 < fS,0 < 1) were synthesized. Both conventional linearization and nonlinear least-squares methods were applied to estimate reliable values of the reactivity ratios for S and DMAEA radical polymerization. The calculated values of the reactivity ratios (rDMAEA = 0.25 and rS = 1.15) perfectly fitted the drift in monomer feed ratio versus conversion, showing a gradient distribution along the copolymer chains. The self-assembling behavior of the copolymers in the aqueous medium was investigated by dynamic light scattering and small-angle neutron scattering over a wide range of pH, temperature, and salt concentration. These block-gradient copolymers show reversible self-association into micelle-like structure (Dh ∼ 20 nm) in aqueous solutions triggered by both pH and temperature

International audience; The self-assembly thermodynamics of pH-sensitive di-block and tri-block gradient copolymers of acrylic acid and styrene was studied for the first time using isothermal titration calorimetry (ITC) and dynamic light scattering (DLS) performed at varying pH. We were able to monitor each step of micellization as a function of decreasing pH. The growth of micelles is a multi-stage process that is pH dependent with several exothermic and endothermic components. The first step of protonation of the acrylic acid monomer units was accompanied mainly by conformational changes and the beginning of self-assembly. In the second stage of self-assembly, the micelles become larger and the number of micelles becomes smaller. While solution acidity increases, the isothermal calorimetry data show a broad deep minimum corresponding to an exothermic process attributed to an increase in the size of hydrophobic domains and an increase in the structure's hydrophobicity. The minor change in heat capacity (ΔCp) confirms the structural changes during this exothermic process. The exothermic process terminates deionization of acrylic acid. The pH-dependence of the ζ-potential of the block gradient copolymer micelles exhibits a plateau in the regime corresponding to the pH-controlled variation of the micellar dimensions. The onset of micelle formation and the solubility of the gradient copolymers were found to be dependent on the length of the gradient block.

The potential use of polyester polymeric nanoparticles (NPs) as drug nanocarriers is well-documented. Nevertheless, structural changes due to hydrophobic drug loading and release have been rarely explored. Herein, we have used static and dynamic light scattering (SDLS), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and cryo-TEM to probe how the entrapment of a hydrophobic drug molecule changes the nanoparticles feature. The presence of the hydrophobic drug molecule modifies the inner structure of the NPs. The polymeric assemblies are characterized by differences in their densities (∼ 0.06 g cm-3 for poly(D,L-lactide) – PLA or poly(D,L-lactide-co-glycolide – PLGA) and 0.46 g cm-3 for poly[(butylene succinate)-co-(butylene dilinoleate)] − PBSBDL). They are thus water swollen in the drug-free condition. The NPs were further prepared by using the same polyesters and given amounts of the poorly water-soluble drug paclitaxel (PTX). The density (dNP), RG (radius of gyration), RH (hydrodynamic radius), RG/RH and R (contrast radius) have been monitored as a function of the amount of drug loaded. The drug entrapment increased the size of PLA and PLGA NPs. On the other hand, it also promoted the shrinkage of PBSBDL NPs. These observations revealed that changes in the inner structure of soft nanoparticles caused by drug loading is not straightforward and it mainly depends on the strength of van der Waals interactions between the polyester core and the probe which is connected to their chemical composition and hydrophobicity. These findings are crucial to understand the key physicochemical parameters involved in the interactions between drug and polymer that affects the final particle structure and influence its loading, release and degradation.

ACS omega 3(3), 3235 - 3247 (2018). doi:10.1021/acsomega.7b01935, Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) are bioactive lipids with considerable impact in medicine and nutrition. These compounds exert structuring effects on the cellular membrane organization, regulate the gene expression, and modulate various signaling cascades and metabolic processes. The purpose of the present work is to demonstrate the structural features of ω-3 PUFA-containing three-dimensional supramolecular lipid assemblies suitable for pharmaceutical applications that require soft porous carriers. We investigate the liquid crystalline structures formed upon mixing of eicosapentaenoic acid (EPA, 20:5) with the lyotropic nonlamellar lipid monoolein and the formation of multicompartment assemblies. Starting with the monoolein-based lipid cubic phase, double membrane vesicles, cubosome precursors, sponge-type particles (spongosomes), mixed intermediate nonlamellar structures, and multicompartment assemblies are obtained through self-assembly at different amphiphilic compositions. The dispersions containing spongosomes as well as nanocarriers with oil and vesicular compartments are stabilized by PEGylation of the lipid/water interfaces using a phospholipid with a poly(ethylene glycol) chain. The microstructures of the bulk mixtures were examined by cross-polarized light optical microscopy. The dispersed liquid crystalline structures and intermediate states were studied by small-angle X-ray scattering, cryogenic transmission electron microscopy, and quasielastic light scattering techniques. They established that PUFA influences the phase type and the sizes of the aqueous compartments of the liquid crystalline carriers. The resulting multicompartment systems and stealth nanosponges may serve as mesoporous reservoirs for coencapsulation of ω-3 PUFA (e.g., EPA) with water-insoluble drugs and hydrophilic macromolecules toward development of combination treatment strategies of neurodegenerative and other diseases., Published by ACS Publications, Washington, DC

International audience; We report on the self-assembly behavior of poly(2-methyl-2-oxazoline)–block–poly(2-octyl-2-oxazoline) comprising different terminal perfluoroalkyl fragments in aqueous solutions. As reported previously [Eur. Polym. J., 2017, 88, 645-655] such polyphiles can form a plethora of nanostructures depending of the composition and on the way of preparation. Here we report, for the first time, detailed information on the internal structure of the nanoparticles resulting from the self-assembly of these copolymers. Small-angle neutron and x-ray scattering (SANS/SAXS) experiments unambiguously prove the existence of polymersomes, wormlike micelles and their aggregates in aqueous solution. It is shown that increasing content of fluorine in the poly(2-oxazoline) copolymers results in a morphological transition from bilayered or multi-layered vesicles to wormlike micelles for solutions prepared by direct dissolution.In contrast, nanoparticles prepared by dialysis of a polymer solution in a non-selective organic solvent against water are characterized by SAXS method. The internal structure of the nanoparticles could be assessed by fitting of the scattering data, revealing complex core-double shell architecture of spherical symmetry. Additionally, long range ordering is identified for all studied nanoparticles due to the crystallization of the poly(2-octyl-2-oxazoline) segments inside the nanoparticles.

International audience; Shear responsive surfaces offer potential advances in a number of applications. Surface functionalization using polymer brushes is one route to such properties, particularly in the case of entangled polymers. We report on neutron reflectometry measurements of polymer brushes in entangled polymer solutions performed under controlled shear as well as coarse-grained computer simulations corresponding to these interfaces. Here we show a reversible and reproducible collapse of the brushes, increasing with the shear rate. Using two brushes of greatly different chain lengths and grafting densities, we demonstrate that the dynamics responsible for the structural change of the brush are governed by the free chains in solution rather than the brush itself, within the range of parameters examined. The phenomenon of the brush collapse could find applications in the tailoring of nanosensors and as a way to dynamically control surface friction and adhesion.

International audience; The charge transport properties of thin films prepared from colloidal dispersion of polyaniline stabilized by poly(N-vinylpyrrolidone) (PANI/PVP) have been investigated. The electrical characterization of coplanar device comprising of gold electrodes and PANI/PVP film deposited by spin coating served to gain insights into the contact and bulk resistance. The films prepared from PANI/PVP colloidal dispersion show high stability over a large temperature range. Temperature dependent measurements in the range from 90 to 350 K reveal that the charge transport can be described by a three-dimensional variable-range hopping mechanism as the dominant mode in the films. The stability of the films cast from dispersion within a large temperature range opens the possibility of the application as a polymer semiconductor layer in sensors and charge-transport interlayer in organic solar cells.

The present work is devoted to the study of interactions between a cationic polyelectrolyte and an anionic surfactant in the solution bulk and at the water/air and water/oil interfaces. For this purpose surface and interfacial tensions, zeta potential, ellipsometry and dynamic light scattering (DLS) were used to describe the formation of complexes of polyallylamine hydrochloride (PAH) and sodium dodecyl sulphate (SDS). Surface and interfacial tension results are supported by zeta potential measurements and aggregation size measurements via DLS. Due to electrostatic binding of dodecyl sulphate anions to the positive charges of the polyelectrolyte chains the resulting complexes become more hydrophobic. At the 1:1 ratio of PAH:SDS the complexes precipitate and become recharged due to the additional hydrophobic binding of SDS ions. The complexation leads to a depletion of surfactant and hence to an increase in surface and interfacial tensions.

International audience; The MRCI/CBS computational protocol was employed to describe the low-lying electronic states of CF2 in excellent agreement with experiment. Also of interest for modeling the fluorocarbon plasmas are the difluorocarbene ions, and the geometries, adiabatic excitation energies and orbital characteristics of their electronically excited states were established. Most of the transitions leading to the excited states were found to be monoelectronic and, for the dipole-allowed ones, the oscillator strengths and radiative lifetimes were predicted to aid in the spectroscopic studies.

International audience; Using 1H and 13C NMR, FT IR spectroscopy together with quantum mechanical DFT calculations, we show that tetraethyl p-tert-butylcalix[4]arene tetraacetate (1) forms a stable equimolecular complex with proton in the form of hydroxonium ion in acetonitril-d3. Protons for this complex were offered by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and converted to hydroxonium ions by traces of water. The complex 1.H3O+ adopts a slightly asymmetric conformation, which is distinctly more cone-like than ligand 1. According to spectral evidence, the hydroxonium ion H3O+ is bound mainly to three of the phenoxy oxygen atoms of 1 by strong hydrogen bonds leaving the ester carbonyl groups, which are the usual coordination site for metal cations, free. Theoretical DFT calculations support the bonding to phenoxy oxygen atoms but slightly prefer a structure with one of the carbonyls being involved in the coordination.

International audience; This chapter reviews the methods that employed to form well‐defined gradient or block‐gradient copolymers. Gradient copolymers with sufficiently sharp gradient profiles can be considered ‘fuzzy’ block copolymers, and they may exhibit self‐organization and nanostructuration both in bulk and in solution. Gradient copolymers can be used potentially in many fields for example, as compatibilizers they help blend immiscible polymers by reducing the interfacial tension of each homopolymer domain, reinforcing agents, damping materials, thermoplastic elastomers, and biocompatible materials. One way of preparing gradient copolymers is by controlled radical polymerization with a reversible addition fragmentation chain transfer (RAFT). Copolymerization conducted under RAFT conditions can generate copolymers with targeted compositions and controlled architectures. Semi‐batch copolymerization, called ‘forced gradient copolymerization’, is employed to tweak the gradient copolymers by continuously introducing one of the comonomers to the polymerization mixture during the reaction, often using syringe pump.

International audience; The paper focuses on the effects of polymorphism on photodegradation of isotactic polypropylene. The starting polymer was modified by a specific α-nucleating agent, 1,3;2,4-bis(3,4-dimethylbenzylidene)sorbitol, by a specific β-nucleating agent, N,N′-dicyclohexylnaphthalene-2,6-dicarboxamide, or their combination. Samples prepared by compression moulding were then exposed to UV-irradiation in the interval from 0 to 240 h. The differences in morphology were reflected in different photooxidative behaviour. Infrared spectroscopy showed that neat polypropylene was the most sensitive to photooxidation and the sample modified solely by the β-nucleating agent was the least sensitive. The remaining two samples exhibited an intermediate sensitivity. Differential scanning calorimetry revealed that the UV-exposure led to gradual changes in crystallization mechanism specifically asserting in individual materials. This behaviour was ascribed to homogeneous nucleation of partly degraded macromolecules. Possible changes of the nucleating agent itself during UV-exposure were also discussed.

The potential of self-assembled nanoparticles (NPs) containing the fine tunable pH-responsive properties of the hydrophobic poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) core and the protein repellence of the hydrophilic poly[N-(2-hydroxypropyl)methacrylamide] (PHPMA) shell for in vitro cytostatic activity has been explored on cancer cells. The amphiphilic diblock copolymer poly[N-(2-hydroxypropyl)methacrylamide]-b-poly[2-(diisopropylamino)ethyl methacrylate] (PHPMA-b-PDPA) synthesized by a reversible addition–fragmentation chain transfer (RAFT) technique allows for excellent control of the polymer chain length for methacrylamides. The PHPMA-b-PDPA block copolymer dissolved in an organic solvent (ethanol/dimethylformamide) undergoes nanoprecipitation in phosphate buffer saline (PBS, pH [similar] 7.4) and self-assembles into regular spherical NPs after solvent elimination. The NPs’ structure was characterized in detail by dynamic (DLS), static (SLS) and electrophoretic (ELS) light scattering, small angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (cryo-TEM). The PHPMA chains prevented the fouling of proteins resulting in a remarkable stability of the NPs in serum. On decreasing pH the hydrophobic PDPA block becomes protonated (hydrophilised) in a narrow range of pH (6.51 < pH < 6.85; ΔpH [similar] 0.34) resulting in the fast disassembly of the NPs and chemotherapeutic drug release in a simulated acidic environment in endosomal and lysosomal compartments. A minimal amount of drug was released above the threshold pH of 6.85. The in vitro cytotoxicity studies showed an important increase in the activity of the NPs loaded with drug compared to the free drug. The particle\'s size below the cut-off size of the leaky pathological vasculature (less than 100 nm), the excellent stability in serum and the ability to release a drug at the endosomal pH with concomitant high cytotoxicity make them suitable candidates for cancer therapy, namely for treatment of solid tumours exhibiting high tumor accumulation of NPs due to the Enhanced Permeability and Retention (EPR) effect.

cited By 1; International audience; The effect of temperature on self-assembly of a novel type of amphiphilic ionic copolymers comprising a hydrophilic poly(acrylic acid) PAA block and an amphiphilic poly(acrylic acid)-grad-poly(styrene) PAA-grad-PS copolymer block has been studied by Small Angle Neutron and Dynamic Light Scattering (SANS, DLS). The polymers have been synthesized using direct Nitroxide-Mediated Polymerization (NMP) as described elsewhere and proved to be capable of formation of the equilibrium (dynamic) micelles responsive to variations in pH and ionic strength of the solution. We have demonstrated that an increase in temperature from 20 to 80°C has almost no influence if the assembly occurs at pH∼6 in a wide range of salt concentration. Under these conditions stable micelle aggregates are formed. At pH∼6.9 virtually no aggregation occurs at any temperature in salt-free solution, whereas at 1M salt concentration we observed an appearance of the correlation peak in the scattering curves and an increase in hydrodynamic radius in dilute solutions evidencing self-association of polymer chains. The magnitude of the correlation peak increases upon an increase in temperature. This behaviour may be attributed to the combined effect of temperature on the ionization constant and on the strength of hydrophobic interactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

International audience; A novel tin-based POSS analogue, butylstannoxane dodecamer, was incorporated as chemically active nanofiller in epoxy resins and achieved a considerable anti-oxidative activity already near 0.05 wt% and very high activity near 1 wt%. The amino-functional nanofiller, which bonds as a linear segment, displayed a high reactivity towards the resin components during cure and was very poorly extractable. Interestingly, at elevated temperatures, the stannoxane nanofiller, whose functional substituents are attached by ionic bonds, displays a considerable short-range mobility in the matrix, and in course of a nano-phase-separation process, rearranges and polymerizes to needle-like nano-domains. This effect leads to additional crosslinking in the nanocomposite. This ``solid-phase nano-precipitation'' does not occur under oxidative conditions, where the nanofiller preferentially undergoes crosslinking with matrix chains and is thereby immobilized. Nanocomposite synthesis, characterization and the concentration dependence of the nanofiller effect are presented.

International audience; Hybrid organic-inorganic epoxies containing the heavier POSS homologue, n-butylstannoxane dodecamer, incorporated as an inert block, as a linear unit, and as a network junction were prepared. This nanometer-sized inorganic cage is especially attractive because of its chemical reactivity (besides mechanical matrix reinforcement). It can undergo oxidative cross-linking reactions with the matrix, or at elevated temperature in the absence of air, it can oligomerize to larger nanodomains, thus generating additional chemical cross-links. The influences of the bonding situation of the stannoxane cages on the hybrid resins' morphology, mechanical properties, and on the cages' chemical activity were studied. The highest reactivity was observed in the case of the linearly bonded cages, which also can achieve unusual short-range mobility in the matrix at high temperatures. This mobility was found to be a result of reversible oxonium ionic bonds to the linear units. The branching stannoxane units display a fair antioxidative reactivity in the matrix, which is nevertheless markedly smaller than in the case of the linear ones. On the other hand, the branching cage achieves the highest mechanical reinforcement of the matrix. The nonbonded stannoxane displays macroscopic phase separation at concentrations above 4 wt % and does not reinforce the matrix markedly, but at low concentrations, it is highly efficient in counteracting the oxidative degradation of the matrix. The effect of the stannoxane cages was also systematically compared with the effect of similarly incorporated POSS cages in the same matrix and in general.

cited By 31; International audience; A novel type of amphiphilic ionic copolymer comprising a hydrophilic poly(acrylic acid) (PAA) block and an amphiphilic poly(acrylic acid)-grad-poly(styrene) (PAA-grad-PS) copolymer block was synthesized using a one step direct nitroxide-mediated polymerization (NMP). A strong influence of the macroinitiator on the values of the reactivity ratios of the co-monomers is confirmed by 1H NMR. The aggregation behaviour of the copolymers in the aqueous medium was studied by small-angle neutron scattering (SANS) and dynamic light scattering (DLS) and by transmission electron microscopy (TEM) in a wide range of pHs and ionic strengths. It has been demonstrated that PAA-b-(PAA-grad-PS) copolymers are soluble in alkaline water at room temperature without the special experimental procedures (addition of co-solvent, heating, etc.) that are usually required for solubilisation of classical PAA-b-PS diblock copolymers. The self-assembly of the PAA-b-(PAA-grad-PS) copolymers into nano-scale aggregates at low/moderate pH and/or high ionic strength was demonstrated by SANS and DLS experiments. The SANS spectra for the copolymer solution exhibit a correlation peak pointing to the formation of micelles with repulsive coronae. TEM images indicate that the micelles have an approximately spherical shape and exhibit a wide size distribution. Our results prove, that in contrast to "frozen" aggregates formed by PAA-b-PS copolymers in aqueous media, the micelles of PAA-b-(PAA-grad-PS) amphiphilic copolymers exhibit "dynamic" pH-responsive properties, i.e. they can reversibly change their aggregation number upon a variation in the pH or salinity of the solution. © 2012 The Royal Society of Chemistry.

International audience; Polymer nanocomposites of epoxies with a novel filler, amino-functional butyltin oxide cage (stannoxane), were prepared and characterized. The nanofiller displays a promising antioxidizing effect, besides mechanical matrix reinforcement. The reinforcement can be assigned to physical interactions among the polymer bonded nanofiller. Moreover, the stannoxane cage undergoes a rearrangement to larger poly amino-functional nano-objects at higher temperatures, which highly reduces its extractability: it is practically not extractable from the nanocomposites in most cases. This, together with the fact that only a few weight percent are needed to achieve an optimal effect, makes it attractive as an antioxidative stabilizer. Epoxy stannoxane nanocomposite synthesis, stannoxane reactivity and dispersion (morphology via TEM and SAXS), as well as the nanofiller effect on mechanical properties (DMTA) and on thermal stability are discussed. A brief comparison is drawn between the stannoxanes and the previously investigated POSS nanofiller.

10 pages; International audience; We have investigated self-organization of polymers with surfactants through solvent shifting process resulting in formation of stable and uniform nanoparticles. We studied polymeric nanoparticles made of poly(methylmethacrylate) and of polystyrene dispersed in water. The dispersion was prepared by a fast mixing of a solution of the polymers with a solution of several ionic and nonionic surfactants in pure water. We observed the formation of well defined nanoparticles by light scattering, small-angle neutron scattering (SANS), and cryogenic transmission electron microscopy (Cryo-TEM) methods. The study shows how nanoparticle properties are changed by the chemical composition of surfactants, molar mass of polymers, concentrations of both components and finally, by variations in method of nanoparticles preparation. Dynamic light scattering (DLS) and static light scattering (SLS) provide the hydrodynamic radii and radii of gyration for selected types of nanoparticles. Cryo-TEM experiments prove that the nanoparticles have good spherical shape. Analysis of SANS data and Cryo-TEM micrographs suggest that the prepared particles are composed of polymer and surfactant that are evenly distributed.

7 pages; International audience; The possibility of electric field induced phase transitions in soft matter systems was studied by means of small-angle X-ray (SAXS) and neutron (SANS) scattering measurements. By dissolving a diblock copolymer PS-b-PEP (polystyrene-block-poly(ethylene-co-propylene)) in a mixture of cyclohexane (CH) and dimethylformamide (DMF), it was possible to create a liquid 3D cubic structure in which spherical microdomains of DMF were embedded into a liquid CH (major component) matrix with the liquid-liquid interfaces covered by PS-b-PEP diblock copolymer chains. When sited under an external electric field, the experimental SAXS and SANS results revealed that the initial self-organized 3D cubic structure is converted into an hexagonal arrangement. The order-to-order transition was reached by the application of a relatively low dc electric field, ∼1.25 kV/mm. The electric field generates dipole moments in DMF-rich spherical microdomains that are deformed and further interconnected, leading to the formation of the hexagonal packed cylinders. The electric field strength Et needed to induce such transition depends on the magnitude of the generated dipole moment in the DMF-rich spherical microdomains and hence depends on their size and dielectric contrast irrespective of the surrounding liquid. The latter must have the lower dielectric constant for the transition to occur. Et also increases with increasing block copolymer concentration. The chain statistics does not change at the transition and always corresponds to that of a polymer in good solvent. The HEXcylinders phase developed under external electric field is unstable, and as soon as the field is switched off, the cylinders undergo an order-to-order transition back to the cubic phase. Finally, another HEX-cylinders phase thermodynamically stable without electric field was created by dissolving a PS-b-PI diblock copolymer (polystyrene-block-polyisoprene) in a CH-DMF mixture. In this last case, the structure essentially does not feel the presence of an electric field of the same magnitude.

International audience; Electronic transitions of Pr3+ ions in Ga-Ge-Sb-Se glasses corresponding to emissions in the infrared region were studied by means of absorption and emission spectroscopies and fluorescence lifetimes measurements. Transition probabilities, radiative lifetimes, branching ratios, and quantum efficiencies of most of the emission transitions including the infrared ones occurring around 1.3, 1.7, and 2.4 μm were estimated based on a standard Judd-Ofelt analysis.

International audience; Photoinduced reversible switching of charge carrier mobility in conjugated polymers was studied by theoretical and experimental methods. The quantum chemical calculations showed that the presence of dipolar species in the vicinity of a polymer chain modifies the on-chain site energies and consequently increases the width of the distribution of hopping transport states. The influence of photoswitchable charge carrier traps on charge transport was evaluated by current-voltage measurement and by impedance spectroscopy method. It was found that deep traps switchable by photochromic reaction may significantly control the transport of charge carriers, which is exemplified as a significant decrease of the current and increase of parallel resistance measured by impedance spectroscopy.

The conductivity of DNA covalently bonded to a gold surface was studied by means of the STM technique. Various single- and double-stranded 32-nucleotide-long DNA sequences were measured under ambient conditions so as to provide a better understanding of the complex process of charge-carrier transport in natural as well as chemically modified DNA molecules. The investigations focused on the role of several features of DNA structure, namely the role of the negative charge at the backbone phosphate group and the related complex effects of counterions, and of the stacking interactions between the bases in Watson-Crick and other types of base pairs. The measurements have indicated that the best conductor is DNA in its biologically most relevant double-stranded form with Watson-Crick base pairs and charged phosphates equilibrated with counterions and water. All the studied modifications, including DNA with non-Watson-Crick base pairs, the abasic form, and especially the form with phosphate charges eliminated by chemical modifications, lower the conductivity of natural DNA.

International audience; Using 1H and 13C NMR spectroscopy, the interaction of tetrapropoxy-p-tert-butyl-calix[4]arene (1) with H3O+ ions produced by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and traces of water was studied in nitrobenzene-d5. It was shown that 1 readily forms an equimolecular complex with H3O+. The equilibrium constant K of its formation is 2.6 at 296 K. Exchange between bound and free 1 is fast even under mild excess of HDCC, the correlation time Τex being about 0.13 ms. NMR shows that H3O+ is bound to the aryl-oxygen atoms and this binding forces the calixarene cup to adopt a more open and symmetrical conformation. This conclusion is in a full accord with high precision quantum DFT calculations which find one structure of the complex corresponding to a global energy minimum, in which the H3O+ ion is bound to three of the oxygen atoms by strong hydrogen bonds and to the remaining oxygen by two weaker hydrogen bonds. The calixarene part is forced into a C4 symmetrical opened form. When stored for weeks, the complex gradually transforms into other forms, most probably its hydrates, according to spectral evidence and DFT calculations.

11 pages; International audience; Well-defined polystyrene-block-poly(styrene-co-acrylonitrile) PS-block-P(S-co-AN) and poly(styrene-co-acrylonitrile-co- 5-vinyltetrazole) PS-block-P(S-co-AN-co-5VT) block copolymers with various content of acrylonitrile units in the statistical block were synthesized by nitroxide mediated radical polymerization (NMRP) and post-functionalized using efficient ''click" chemistry process. In the second step, acrylonitrile units were successfully modified using 1,3-dipolar cycloaddition (''click" chemistry) type polymer analogue reaction. The original pristine diblock copolymers can be molecularly dissolved in THF and dioxane while the ''tetrazolated" versions aggregate to clusters as determined by dynamic light scattering (DLS). Small-angle X-ray scattering (SAXS) and Transmission Electron Microscopy (TEM) revealed ordered lamellar morphology with interlamellar spacing d = 60 nm increasing to d = 80 nm for ''tetrazolated" diblock copolymers. The morphological features of diblock copolymer thin layers observed by Atomic Force Microscopy (AFM) depend on the tunable content of both acrylonitrile and 5-vinyltetrazole units and on the quality (polarity) of the solvents used.

3 pages; International audience; We studied the micelle formation of a diblock copolymer of styrene and ethylene oxide in mixtures of 2,6- dimethylpyridine (2,6-lutidine) and water. Micelles are formed in a broad solvent composition range with a volume fraction of water ranging from 0.05 to 0.85, where neither polystyrene nor polyethylene oxide homopolymers are soluble. The diffusion behavior of pure solvent mixtures and in solutions of copolymer micelles is reported. In LTD/water mixtures, two diffusive processes corresponding to self-difusion and two modes belonging to mutual diffusion and diffusion of solvent clusters have been found. In copolymer solutions, the mode of copolymer micelle diffusion replaces the mode of solvent cluster diffusion. Quasielastic light scattering, small-angle neutron scattering, and pulsed-field gradient NMR have been employed in our study.

International audience; Using 1H and 13C NMR together with quantum mechanical DFT calculations, we show that p-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (1) forms a stable equimolecular complex with proton in the form of hydroxonium ion in nitrobenzene-d5. Protons were offered by hydrogen bis(1,2-dicarbollyl) cobaltate (HDCC) and converted to hydroxonium ions by traces of water. The complex 1.H3O+ adopts a slightly asymmetric but rapidly motionally averaged conformation, which is distinctly more cone-like than ligand 1. The hydroxonium ion H3O+ is bound partly to thiocarbonyl sulphur atoms and partly to phenoxy oxygen atoms of 1 by strong hydrogen bonds and other electrostatic interactions.

International audience; In the quest for suitable materials for hyperthermia we explored the preparation and properties of nanoparticles of Co ferrite. The material was produced by coprecipitation from water solution of Co and Fe chlorides and afterwards annealed at 400, 600 and 800 °C. The resulting particles were characterized by XRD, TEM, Mössbauer spectroscopy, and dc and ac magnetometry. The heating experiments in ac magnetic fields of various amplitudes were performed with diluted systems of particles suspended in agarose gel and the results were interpreted on the basis of the ac magnetic losses measured at various temperatures. The increase of magnetic losses and consequently of the heating efficiency with increasing temperature is explained by the strong dependence of the constant of magnetocrystalline anisotropy of Co ferrite on temperature.

We report in this work the preparation and characterization of hybrid materials from a novel tin(IV) alkoxodimer of formula [Sn(OPri)2(O2CC(CH3)CH2)2]2 (OPri = (CH3)2CHO) whose structure has been determined by X-ray diffraction and NMR spectroscopy. This molecule has been used as a nanobuilding block in the preparation of new hybrid materials by combining it with several organic monomers, like methyl methacrylate, ethyl acrylate and styrene, at different molar ratios. The obtained polymers have been characterized by several techniques. The results show that the dimer is incorporated in the polymer network by organic bonds that cross-link the polymer chains very efficiently. Consequently, the incorporation of the cluster has improved the thermal properties of the parent polymer allowing their modulation by adjusting the concentration of the cluster.

Continuous-wave CO2 laser irradiation into gaseous mixture of triethylborate and diethoxy(dimethyl)silane represents a very feasible way of direct heat-induced conversion of two precursors, the one with the Si OR and the other with the B OR bonds, to the nanostructured polyborocarbosiloxane phase. These materials contain Si O B, SiO2Xn ( n = 1 , 2; X = C, Si), SiO3X (X = Si, C), SiO4, B(OSi)3, B(OB)3−x(OSi)x and BO3 configurations, possess Si C and B C bonds, have spongy morphology, high specific area and high thermal stability.

International audience; A three-dimensional Voronoi tessellation of folded proteins is used to analyzegeometrical and topological properties of a set of proteins. To each amino acid is associated a centralpoint surrounded by a Voronoi cell. Voronoi cells describe the packing of the amino acids. Specialattention is given to reproduction of the protein surface. Once the Voronoi cells are built, a lot oftools from geometrical analysis can be applied to investigate the protein structure; volume of cells,number of faces per cell, and number of sides per face are the usual signatures of the proteinstructure. A distinct difference between faces related to primary, secondary, and tertiary structures hasbeen observed. Faces threaded by the main-chain have on average more than six edges, whereas thoserelated to helical packing of the amino acid chain have less than five edges. The faces on the proteinsurface have on average five edges within 1% error. The average number of faces on the protein surfacefor a given type of amino acid brings a new point of view in the characterization of the exposition to thesolvent and the classification of amino acid as hydrophilic or hydrophobic. It may be a convenient toolfor model validation.

cited By 36; International audience; We demonstrate the possibility of reversible pH-controlled sol-gel transition in aqueous solution of associating amphiphilic triblock copolymer poly(styrene-grad-acrylic acid)-b-poly(acrylic acid)-b-poly(styrene-grad-acrylic acid), (PS-grad-PAA)-b-PAA-b-(PS-grad-PAA), synthesized via nitroxide-mediated (NM) radical copolymerization. The presence of pH-sensitive co-monomer units of the acrylic acid in the terminal blocks ensures the dynamic nature of the styrene-rich hydrophobic nano-domains which are formed at low pH. At small polymer concentrations the association triggered by lowering the pH gives rise to flower-like micelles stabilized by partially ionized PAA coronae. The pH-controlled association was monitored by DLS-titration and manifested in the evolution of a correlation peak in the SANS spectra. The resulting copolymer aggregates were visualized by TEM, which confirmed the spherical shape of the dense styrene-rich domains. Above the micelle overlap concentration a decrease in pH provokes macroscopic gelation. Here the styrene-reach domains perform as cross-links in the transient network. The pH-triggered sol-to-gel transition is manifested in an abrupt and strong (up to 3 orders of magnitude) increase in the zero-shear viscosity and in a characteristic change in the frequency dependence of the storage and loss moduli. The discovered effect can be used for efficient pH-control of the rheological properties of aqueous solutions. © 2011 The Royal Society of Chemistry.

6 pages; International audience; A diblock copolymer dissolved in a mixture of partially miscible solvents creates a self-organized microemulsion with a morphology that depends on the numerous parameters of the system. We discuss one particular case of spherical particles (containing the minority solvent) forming a hard gel with cubic structure and demonstrate using high-resolution synchrotron scattering experiments that the self-organized solution has a BCC structure. After fitting one- and two-dimensional form factors we extract from the data the one- and two-dimensional structure factors, S(q) and S(q,j). The experimental S(q) corresponds almost quantitatively, up to the 9th order Bragg peak, to that calculated numerically for a randomly-oriented, finite-size BCC crystal. S(q,j) contains a large number of reflections that allow the structure to be identified more exactly as a twin BCC morphology with some imperfections. Examination of the dependence of the structural parameters on polymer concentration reveals that the dilution law predicted theoretically for the center-to-center distance of the spheres is confirmed experimentally while the size of the spherical objects does not follow theoretical predictions due to chain extension with increasing concentration.

Polystyrene-block-polyisoprene with hydrogenated polyisoprene block (Shellvis 50) was sulfonated to a high degree (up to 42 mol% of styrene units) using acetyl sulfate as sulfonation agent in various chlorinated solvents. Membranes were prepared from the tetrahydrofuran solution of the sulfonated copolymer by casting. The membranes were characterized by conductivity and SAXS measurements.