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The structural organization of chitosan, a cationic polyelectrolyte, in aqueous solutions of high ionic strength, is investigated by quasi-elastic light scattering and wet scanning transmission electron microscopy. The formation of submicrometric chain aggregates driven by hydrophobic interactions is evidenced. These heterogeneities are at the core of the multiscale morphology of physical hydrogels processed from this polysaccharide. Therefore, a close structural relationship exists between the initial solution and the final hydrogel.

A general, rapid, and undemanding method to generate at will functional oil-filled nanocapsules through nanoprecipitation is reported. On the basis of polymer and hexadecane/water/acetone phase diagrams, the composition can be set so that polymer chains preferentially stick at the interface of the oil droplets to create nanocapsules. The nanocapsules can be decorated with biorelevant molecules (biotin, fluorescent tags, metal nanoparticles) within the shell and loaded with hydrophobic molecules in a simple one-pot procedure.

We report here on a one-pot construction of oil-filled hierarchical capsular assemblies using the nanoprecipitation technique. Relying on multicomponent phase diagrams, we show that simultaneous and/or sequential nanoprecipitations involving polymer combinations can be precisely programmed to design a new class of mixed/multilayered multicomponent nanocapsules, with a precise control of the dimensions, shell thickness/composition, and spatial distribution of the building blocks. The simplicity and tunability of this approach are exemplified here with a library of neutral and ionic polysaccharides giving access to a range of functional multilayered nanocarriers of interest for biomedical applications.

A series of well-defined hybrid block copolymers PMACyPOSS-b-PMMA and PMAiBuPOSS-b-PMMA exhibiting high POSS weight contents have been synthesized by RAFT polymerization and further studied as modifiers for epoxy thermosets based on diglycidyl ether of bisphenol A. The hybrid block copolymers self-assembled within the epoxy precursors into micelles possessing an inorganic core and a PMMA corona. Thanks to the presence of the PMMA blocks that remain miscible until the end of the reaction, curing of the resulting blends afforded nanostructured hybrid organic/ inorganic networks with well-dispersed inorganic-rich nanodomains with diameters on the order of 20 nm. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: [4343][4344][4345][4346][4347][4348][4349][4350][4351][4352] 2011

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International audienceSupramolecular miktoarm stars (AB(2) type) composed of poly (methyl methacrylate)-polystyrene(2) (PM MA-PS. poly(isoprene)-polystyrene2 (PI-PS2), and poly(vinyl acetate)-polystyrene, (PVAc-PS2) were successfully synthesized by assembling reversible addition fragmentation chain transfer (RA FT)-polymerized chains bearing hydrogen-bonding heterocomplementary associating units To this end, thymine and diaminopyridine-Functionalized chain transfer agents were designed to efficiently mediate the polymerization of vinyl acetate, methyl methacrylate. isoprene, and styrene The selective associations of the resulting hydrogen-bonding macromolecular building blocks PVAc/PS. PI/PS, and PMMA/PS were demonstrated by H-1 NMR in CDCl3 solutions Miktoarm stars formation in the bulk was also confirmed by transmission electronic microscop

Using dewetting as a characterization tool, we demonstrate that physical properties of thin polymer films can be regulated and tuned by employing variable processing conditions. For different molecular weights, the variable behavior of polystyrene films of identical thickness, prepared along systematically altered pathways, became predictable through a single parameter P, defined as the ratio of time required over time available for the equilibration of polymers. In particular, preparation-induced residual stresses, the corresponding relaxation times as well as the rupture probability of such films (of identical thickness) varied by orders of magnitude following scaling relations with P. Our experimental findings suggest that we can predictably enhance properties and hence maximize the performance of thin polymer films via appropriately chosen processing conditions.