Synthesis, characterization and applications of pH-responsive core-shell-corona micelles in water

ABC triblock copolymers self-organize into a wide variety of supramolecular structures in the bulk. However, their associative behavior in selective solvents has scarcely been studied. Within the search for new stimuli-responsive supramolecular architectures, our attention focused on a pH-responsive polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) (PS-b-P2VP-b-PEO) triblock copolymer. In addition to the synthesis of monodisperse spherical core-shell-corona (CSC) micelles, the reversibility and the cooperativity of the response to pH variations were studied, morphological transitions were induced and multi-responsive micellar gels were prepared. The micellization mechanism, the structure, the responsiveness and the internal organization of these new nanomaterials were investigated using a combination of transmission electronic microscopy, atomic force microscopy, light scattering, small-angle neutron and X-ray scattering, nuclear magnetic resonance and rheology. Finally, efforts were geared towards potential applications. The ability of PS-b-P2VP-b-PEO CSC micelles to encapsulate and release hydrophobic species was probed and gold nanoparticles were successfully synthesized within the P2VP layer of spherical and cylindrical micelles, which acted as nanoreactors.Les copolymères triséquencés ABC s’auto-organisent et forment une large gamme de structures supramoléculaires en phase solide. Cependant, peu d’études portent sur leur comportement associatif induit par des solvants sélectifs. Dans le cadre de la recherche de nouvelles architectures supramoléculaires sensibles aux stimuli externes, nous avons entrepris l’étude d’un copolymère triséquencé sensible au pH : polystyrène-b-poly(2-vinylpyridine)-b-poly(oxyde d’éthylène). Outre la synthèse de micelles sphériques de type CSC, le caractère réversible et coopératif de la réponse au pH a été étudié, ainsi que l’induction de transitions morphologiques et la préparation de gels micellaires sensibles à la température et au pH. Le mécanisme de micellisation, les paramètres structuraux, la sensibilité aux stimuli ainsi que l’organisation interne de ces nouveaux nanomatériaux ont été étudiés par une combinaison de microscopies électronique à transmission et à force atomique, diffusion lumineuse, diffusion de neutrons et rayons X aux petits angles, résonance magnétique nucléaire et rhéologie. Enfin, des applications ont été envisagées : la capacité des micelles CSC à encapsuler et libérer des composés hydrophobes a été testée et des nanoparticules d’or ont été synthétisées avec succès au sein de ces nanoréacteurs, c’est-à-dire dans la couche de P2VP des micelles sphériques et cylindriques

LCA discussion on diffractive intraocular lenses: a new optical design to correct chromatic aberration

Methods: The effects of Abbe number and the topography of different diffractive IOL profiles were evaluated. On the basis of MTF through-focus curves at different light wavelengths (red, blue and green) and for different pupil apertures, polychromatic behavior of various diffractive multifocal IOLs was assessed. Pin-hole effect will also be discussed and addressed with the point of view of chromatic effect. Results: Diffractive multifocal IOLs show chromatic aberration especially along the axis (LCA-longitudinal Chromatic aberration) but also out of the optical axis. These chromatic aberrations are the results of the refractive chromatic properties of the lens, driven by the biomaterial refractive indexes and the IOL diffractive pattern. Refractive effects are mainly controlled by the biomaterial Abbe number while diffractive effects are controlled by the topography of the diffractive pattern. Conclusions: Refractive effects are mainly controlled by biomaterial Abbe number while diffractive effects are controlled by diffractive pattern topography. The insertion of a multifocal diffractive lens following crystalline lens extraction may significantly modify the chromatic aberration of the pseudophakic eye. Chromatic aberrations induce vision losses due to sharpness reduction of (any) object edges. The contrast sensitivity as well as the visual acuity are then reduced. This fact has especially been proven with measurements on optical benches. Moreover, diffractive and refractive effects act in an opposite ways and can in principle be compensated. However rules to creates an achromatic lens based on refractive-diffractive principles are quite complex

Topography and Longitudinal Chromatic Aberration characterizations of Refractive-Diffractive Multifocal IOLs

Purpose Most optical systems present chromatic aberration quantified along the optical axis by the longitudinal chromatic aberration (LCA). LCA is controlled by the biomaterial Abbe number combined with diffractive effects, driven by the IOL topography. This paper experimentally aims at describing in vitro the effect of LCA in diffractive multifocal IOLs, with the help of dedicated optical benches and topographic characterization. Setting Centre Spatial de Liege. Design Optical and topology analysis of various Multifocal diffractive intraocular lenses. Methods Seven diffractive multifocal lenses, available on the market and exhibiting different diffractive profiles, made from various biomaterials, were characterized under different wavelengths. Results Through-focus Modulation Transfer Function (MTF) curves and IOL diffraction efficiency depends on the incident light wavelength. In this paper, we investigated the topology properties of various Multifocal intraocular lenses and correlated their characteristics to their optical behavior for various wavelengths. Chromatic properties and their origins were then compared. As expected, diffractive and refractive effects were found to act in opposite ways, and could be partially or completely compensated. Conclusions The longitudinal chromatic aberration of each of the lenses was evaluated in vitro. In most of the MIOLs studied, some of the foci were found to be refractive, while others were diffractive. Although the results were not extrapolated to clinical relevance , it was shown, in some of the cases, that LCA could be fully compensated

pH Dependence of the morphology of aqueous micelles formed by polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) copolymers

The morphology of micelles formed by two polystyrene-block-poly(2-vinylpyridine)- block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) copolymers was studied in water by dynamic light scattering and transmission electron microscopy. Spherical micelles were observed that consist of a PS core, a P2VP shell and a PEO corona. The characteristic size of core, shell and corona depends on the copolymer composition. An important increase in micellar size occurs at pH < 5 as a result of P2VP block protonation. The reversibility of this pH effect depends on copolymer composition, too. The conformation of the PEO block plays an important role in this pH driven morphological transition.SUPERNET progra