A series of double hydrophilic block copolymers DHBCs has been synthesized by controlled radical polymerization (Figure 1). Poly(ethylene oxide)-b-poly(acrylic acid) PEO-b-PAA was prepared by ATRP in acetone. PEO-b-PAA and PEO-b-Poly(N-isopropyl acrylamide) PEO-b-PNIPAM were prepared by RAFT using a PEO-based dithiobenzoate macro-RAFT agent, in water and dioxane respectively. Poly(poly(ethylene glycol) methyl ether acrylate)-b-PAA PmPEGA-b-PAA was prepared by RAFT in water using a trithiocarbonate RAFT agent. Poly(acrylamide)-b-PAA PAM-b-PAA and PAM-b-poly(3-acrylamidopropyl)trimethylammonium chloride) PAM-b-PAPTAC were prepared by RAFT/MADIX using xanthate as control agent, in water/ethanol for the PAM block and directly in water for the second block. The block copolymers have been characterized by SEC, pH titration, conductimetry, and capillary electrophoresis (CE).The reversible formation of micelles by variation of temperature in the case of PEO-b-PNIPAM, or by the mixing of polyelectrolyte DHBCs with a polyelectrolyte of opposite charge in the right range of pH (e.g. anionic PEO-b-PAA associated with cationic oligochitosan) has been studied. The micelles have been characterized by various scattering techniques and CE.Such stimuli-responsive (T, pH, ionic strength) micellar systems have been involved as structuring agents in the synthesis of nanostructured mesoporous silica by sol-gel process. A relationship between the composition of the DHBCs, the composition of the micelles, the experimental conditions of micelle formation and the final mesostructure of the silica materials is foreseen. This strategy has been applied to the preparation of drug-loaded silica for biomedical applications.

L’observation de résistances chez certaines espèces de moustiques aux pesticides synthétiques les plus couramment utilisés a conduit à l’utilisation et au développement d’alternatives efficaces aux insecticides chimiques. Ainsi, l’insecticide d’origine bactérienne Bacillus thuringiensis israelensis (Bti) est devenu pratiquement la seule substance active autorisée pour le traitement des gîtes larvaires de moustiques en milieu naturel en France métropolitaine. Si le Bti est un biolarvicide intéressant, son efficacité dépend de sa présence et de sa rémanence à la surface de l’eau, c’est‐à‐dire là où les larves de moustiques se nourrissent, exclusivement pour certaines espèces anophèles. Le projet de recherche "MicroBti" consiste à étudier deux stratégies de formulation qui permettraient de prolonger la présence de Bti à la surface de l’eau au-delà de quelques jours (à l’exception des eaux usées), pour le traitement des gîtes larvaires.

Gliadins are edible wheat storage proteins well known for their surface active properties1, 2. Although their foaming3 and emulsifying4 capability is useful in food industry, the physical mechanisms of their adsorption at an interface are not well understood and the resulting structure of the protein interfacial films not yet well characterized. In this talk, we will present experimental results on the interfacial properties of acidic gliadin solutions studied over 4 decades of concentrations from 0.01 up to 110 mg/ml.Dynamic pendant drop tensiometry reveals that the surface pressure of gliadin solutions builds up in a multistep process. We show that the series of curves of the time evolution of alpha.time collected at different protein concentrations can be merged onto a single master curve when surface pressure is plotted as a function of alpha.time where t is the time elapsed since the formation of the air/water interface and alpha is a shift parameter that varies with the bulk protein concentration as a power law with an exponent 1.6. The existence of a master curve indicates that the surface pressure is the relevant parameter to characterize the interfaces covered with gliadin proteins.Optical and elastic properties of the interfaces are studied by dilatational rheology and ellipsometry and provide a consistent physical picture of the adsorption processes. Correlated evolutions of ellipsometry and rheological properties show a simple and progressive coverage of the interface by individual proteins at low surface pressure. This stage is followed, at higher surface pressure, by conformational rearrangements of the protein film, which are identified by a strong increase of the dissipative viscoelastic properties of the film concomitantly with an anomalous evolution of its optical profile that we have quantitatively rationalized. In the last stage, at even higher surface pressure, the optical profile is not modified while the elasticity of the film dramatically increases resulting from the gelation of the film due to the formation of intermolecular bonds. [1] J.Ornebro, T. Nylander, A-C Eliasson (2000). Journal of Cereal Science 31, 195-221[2] R. C. A Keller, R. Orsel, R. J. Hamer (1997). Journal of Cereal Science 25, 175-183[3] Martin A. Bos, Bertus Dunnewind, Ton van Vliet (2003). Colloids and Surfaces B 31, 95-105[4] Y.Popineau, F.Pineau, P. Evon, S. Bérot (1999). Nahrung 6, S. 361-367

Controlling the interface between TiO2 nanocrystals and ionic liquids is of high fundamental and applied interest for energy storage and conversion devices. Phase transfer of nanoparticles from a synthesis medium to a processing or an application medium plays a significant role in nanotechnology. Here we demonstrate that surface modification with phosphonic acids bearing cationic end-groups can trigger the phase transfer of TiO2 nanoparticles from an aqueous sol to a typical water-immiscible ionic liquid, [Emim][NTf2]. The transfer involves both the grafting of the phosphonic acid moiety and the exchange of the counter ion of the cationic end-group by NTf2 anions, as demonstrated by solid-state NMR, elemental analysis and independent grafting and ion exchange experiments. Furthermore, the colloidal stability of the TiO2 sols in [Emim][NTf2] strongly depends on the hydrophobic character of the cationic end-groups.

Biological or artificial microswimmers move performing trajectories of different kinds such as rectilinear, circular, or spiral ones. Here, we report on circular trajectories observed for active Janus colloids trapped at the air−water interface. Circular motion is due to asymmetric and nonuni form surface properties of the particles caused by fabrication. Motion persistence is enhanced by the partial wetted state of the Janus particles actively moving in two dimensions at the air−water interface. The slowing down of in plane and out of plane rotational diffusions is described and discussed.

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