Using small-angle neutron scattering to characterize the structure of liposomial and micellar samples: stimuli-responsive and drug effects

Poster (2011, June 22)

Stimuli-responsive triblock copolymer for biomedical applications

Poster (2010, May 25)

Magnetic hybrid micelles based on iron oxide nanoparticles an thermoresponsive block copolymer for biomedical applications

Poster (2009, December 14)

Self-assembly and pH-responsiveness of ABC miktoarm star terpolymers

in Langmuir (2009), 25(1), 107-111

This work deals with the self-assembly in water of ABC miktoarm star terpolymers consisting of hydrophobic poly(-caprolactone), hydrophilic poly(ethylene oxide) (PEO), and pH-sensitive poly(2 ... [more ▼]

This work deals with the self-assembly in water of ABC miktoarm star terpolymers consisting of hydrophobic poly(-caprolactone), hydrophilic poly(ethylene oxide) (PEO), and pH-sensitive poly(2-vinylpyridine) (P2VP). A variety of experimental techniques were used, including dynamic light scattering, transmission electron microscopy, and zeta potential. Special attention was paid to the pH dependency of the supramolecular self-assemblies. A key observation is the capability of the miktoarm terpolymers to form micelles stable over the whole range of pH, although a transition was observed from neutral to highly positively charged nanoobjects upon decreasing pH. [less ▲]

Normal and frictional forces between surfaces bearing polyelectrolyte brushes

in Langmuir (2008), 24(16), 8678-8687

Normal and shear forces were measured as a function of surface separation, D, between hydrophobized mica surfaces bearing layers of a hydrophobic−polyelectrolytic diblock copolymer, poly(methyl ... [more ▼]

Normal and shear forces were measured as a function of surface separation, D, between hydrophobized mica surfaces bearing layers of a hydrophobic−polyelectrolytic diblock copolymer, poly(methyl methacrylate)-block-poly(sodium sulfonated glycidyl methacrylate) copolymer (PMMA-b-PSGMA). The copolymers were attached to each hydrophobized surface by their hydrophobic PMMA moieties with the nonadsorbing polyelectrolytic PSGMA tails extending into the aqueous medium to form a polyelectrolyte brush. Following overnight incubation in 10−4 w/v aqueous solution of the copolymer, the strong hydrophobic attraction between the hydrophobized mica surfaces across water was replaced by strongly repulsive normal forces between them. These were attributed to the osmotic repulsion arising from the confined counterions at long-range, together with steric repulsion between the compressed brush layers at shorter range. The corresponding shear forces on sliding the surfaces were extremely low and below our detection limit (±20−30 nN), even when compressed down to a volume fraction close to unity. On further compression, very weak shear forces (130 ± 30 nN) were measured due to the increase in the effective viscous drag experienced by the compressed, sliding layers. At separations corresponding to pressures of a few atmospheres, the shearing motion led to abrupt removal of most of the chains out of the gap, and the surfaces jumped into adhesive contact. The extremely low frictional forces between the charged brushes (prior to their removal) is attributed to the exceptional resistance to mutual interpenetration displayed by the compressed, counterion-swollen brushes, together with the fluidity of the hydration layers surrounding the charged, rubbing polymer segments. [less ▲]

Fast multiresponsive micellar gels from a smart ABC triblock copolymer

in Angewandte Chemie (International ed. in English) (2007), 46(42), 7988-7992

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and ... [more ▼]

The triblock copolymer PS-b-P2VP-b-PEO undergoes simultaneous micellization and gelation, leading to high-storage-modulus materials that have fast responses to pH value, temperature, ionic strength, and shearing. The gel has a hierarchical structure with spherical core-shell-corona micelles, which, in turn, pack closely into an ordered cubic structure. [less ▲]

Dependence of the structure of core-shell-corona micelles on the composition of water/toluene mixtures

in Polymer (2006), 47(8), 2723-2727

The poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethyleile oxide) triblock copolymer. PS200-b-P2VP(140)-b-PEO590, where the subscripts refer to the average degrees of polymerisation of the ... [more ▼]

The poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethyleile oxide) triblock copolymer. PS200-b-P2VP(140)-b-PEO590, where the subscripts refer to the average degrees of polymerisation of the constitutive blocks, has been dissolved in water/toluene mixtures with a large range of composition, i.e. in (i) toluene added with a small amount of water. (ii) water-in-toluene emulsion forming mixtures, (iii) toluene-in-water emulsion forming mixtures, and (iv) water added with a small amount of toluene. These Solutions have been cast on a carbon-coated copper grid, and the morphology of the dried copolymer deposition has been observed by transmission electron microscopy. Rod-like aggregates with a core-shell-corona micellar structure are formed in cases (i) and (iv). Nevertheless, PEO is the core and PS is the corona in case (i). whereas the reverse situation prevails in case (iv). When an emulsion is the precursor of the dried copolymer aggregates, either onion-like structures (case ii) or vesicles mixed with more complex aggregates are formed (case iii). These structures are thought to reflect the self-organization of the PS200-b- P2VP(140)-b-PEO590 copolymer at the water/toluene interface of the water-in-toluene and toluene-in-water emulsions. respectively. [less ▲]

Tuning the Hydrophilicity of Gold Nanoparticles Templated in Star-Block Copolymers

in Langmuir (2006), 22

We report on a simple procedure to tune the hydrophilicity of hybrid gold nanoparticles. The nanoparticles have been prepared in the core of a poly(ethylene glycol)-block-poly( -caprolactone) (PEG-b-PCL ... [more ▼]

We report on a simple procedure to tune the hydrophilicity of hybrid gold nanoparticles. The nanoparticles have been prepared in the core of a poly(ethylene glycol)-block-poly( -caprolactone) (PEG-b-PCL) five-arm star block copolymer. A hydrophilic corona was then added to these hybrid gold nanoparticles by direct chemisorption of trithiocarbonate-containing poly(acrylic acid) chains. These polymers were synthesized by RAFT polymerization with a trithiocarbonate as the chain-transfer agent. The efficiency of the grafting was evidenced by TEM, AFM, and DLS and by the successful transfer of these nanoparticles from organic solvent to water. [less ▲]

Core-shell-corona micelles: focus on the pH-responsive shell

Conference (2005, October)

Normal and shear forces between a polyelectrolyte brush and a solid surface

in Journal of Polymer Science Part B-Polymer Physics (2005), 43(2), 193-204

The diblock copolymer poly(methyl methacrylate)-b-poly(sodium sulfonated glycidyl methacrylate) (PMMA-b-PSGMA) was end-attached by its hydrophobic block (PMMA) onto mica hydrophobized by a stearic ... [more ▼]

The diblock copolymer poly(methyl methacrylate)-b-poly(sodium sulfonated glycidyl methacrylate) (PMMA-b-PSGMA) was end-attached by its hydrophobic block (PMMA) onto mica hydrophobized by a stearic trimethylammonium iodide (STAI) layer, to form a polyelectrolyte brush immersed in water. With a surface force balance (SFB), we extended earlier measurements between two such brush layers for the case of normal and shear forces at different shear rates, surface separation, and compressions between one mica surface coated with STAI or a STAI-diblock layer against a bare mica surface. After coating one of the surfaces with STAI, a long range attraction that results in a jump into an adhesive flat contact between the hydrophobic and hydrophilic surfaces was observed. A very different behavior was seen after forming the polyelectrolyte brush on the STAI-coated surface. The long range attraction was replaced by repulsion, accompanied by very low friction during shear (ca. three orders of magnitude lower than with adsorbed polyelectrolytes). On further compression, a weak attraction to the adhesive contact was observed. From the final surface-surface contact separation, we deduce that most of the polyelectrolyte diblock brush layer was squeezed out from the gap, leaving the STAI layer and a small amount of the polymer attached to the surface. Stick-sliding behavior was seen while applying shear, suggesting a dissipation mechanism caused by the trapped polyelectrolyte. [less ▲]