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See detailConcomitant adsorption of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers and sodium dodecyl sulfate at the silica-water interface
Vangeyte, Patrick; Leyh, Bernard ULg; De Clercq, C. et al

in Langmuir (2005), 21(17), 7710-7716

Upon addition of silica to aqueous solutions of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers (PEO-b-PCL) and sodium dodecyl sulfate (SDS), adsorption of the solutes occurs at the silica ... [more ▼]

Upon addition of silica to aqueous solutions of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers (PEO-b-PCL) and sodium dodecyl sulfate (SDS), adsorption of the solutes occurs at the silica-water interface. The amount of the adsorbed constituents has been measured by the total concentration depletion method. Small-angle neutron scattering experiments (SANS) have been carried out to investigate the structure of the adsorbed layer. Although SDS is not spontaneously adsorbed onto hydrophilic silica, adsorption is observed in the presence of PEO-b-PCL diblocks, in relation to the relative concentration of the two compounds. Conversely, SDS has a depressive effect on the adsorption of the copolymer, whose structure at the interface is modified. Copolymer desorption is however never complete at high SDS content. These observations have been rationalized by the associative behavior of PEO-b-PCL and SDS in water. [less ▲]

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See detailAdsorption of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers at the silica-water interface
Vangeyte, Patrick; Leyh, Bernard ULg; Rojas, O. J. et al

in Langmuir (2005), 21(7), 2930-2940

The adsorption of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) and poly(ethylene oxide)-b-poly(gamma-methyl-epsilon-caprolactone) copolymers in aqueous solution on silica and glass ... [more ▼]

The adsorption of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) and poly(ethylene oxide)-b-poly(gamma-methyl-epsilon-caprolactone) copolymers in aqueous solution on silica and glass surfaces has been investigated by flow microcalorimetry, small-angle neutron scattering (SANS), surface forces, and complementary techniques. The studied copolymers consist of a poly(ethylene oxide) (PEO) block of M(n) = 5000 and a hydrophobic polyester block of poly(epsilon-caprolactone) (PCL) or poly(gamma-methyl-epsilon-caprolactone) (PMCL) of M(n) in the 950-2200 range. Compared to homoPEO, the adsorption of the copolymers is significantly increased by the connection of PEO to an aliphatic polyester block. According to calorimetric experiments, the copolymers interact with the surface mainly through the hydrophilic block. At low surface coverage, the PEO block interacts with the surface such that both PEO and PCL chains are exposed to the aqueous solution. At high surface coverage, a dense copolymer layer is observed with the PEO blocks oriented toward the solution. The structure of the copolymer layer has been analyzed by neutron scattering using the contrast matching technique and by tapping mode atomic force microscopy. The experimental observations agree with the coadsorption of micelles and free copolymer chains at the interface. [less ▲]

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See detailMixed self-assembly of poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers and sodium dodecyl sulfate in aqueous solution
Vangeyte, Patrick; Leyh, Bernard ULg; Auvray, L. et al

in Langmuir (2004), 20(21), 9019-9028

Interaction of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers with anionic sodium dodecyl sulfate (SDS) has been investigated in aqueous solution. Formation of mixed micelles has ... [more ▼]

Interaction of amphiphilic poly(ethylene oxide)-b-poly(epsilon-caprolactone) copolymers with anionic sodium dodecyl sulfate (SDS) has been investigated in aqueous solution. Formation of mixed micelles has been confirmed by surface tension measurements, whereas the influence of the surfactant on the copolymer self-assembling has been studied by measurement of the 1H NMR self-diffusion coefficients and by small-angle neutron scattering. As a rule, the surfactant decreases the heterogeneity of the micellar structures formed by the copolymer in water. Moreover, increasing the content of SDS results in the increasingly more important extension of the poly(ethylene oxide) (PEO) corona chains and the copolymer micelle deaggregation. The stability of the micelles against SDS increases with the length of the hydrophobic block. Preliminary two-dimensional NMR measurements with nuclear Overhauser enhancement have confirmed the spatial vicinity between SDS and the constitutive blocks of the copolymer. [less ▲]

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See detailAbout the methods of preparation of poly(ethylene oxide)-b-poly(epsilon-caprolactone) nanoparticles in water. Analysis by dynamic light scattering
Vangeyte, Patrick; Gautier, Sandrine; Jérôme, Robert ULg

in Colloids and Surfaces A : Physicochemical and Engineering Aspects (2004), 242(1-3), 203-211

Self-assembly of nonionic amphiphilic poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) and poly(ethylene oxide)-b-poly(γ-methyl-ε-caprolactone) (PEO-b-PMCL) has been studied in water by dynamic ... [more ▼]

Self-assembly of nonionic amphiphilic poly(ethylene oxide)-b-poly(ε-caprolactone) (PEO-b-PCL) and poly(ethylene oxide)-b-poly(γ-methyl-ε-caprolactone) (PEO-b-PMCL) has been studied in water by dynamic light scattering (DLS). The aqueous solutions have been prepared by three methods, i.e., dialysis of solutions in a common organic solvent against water, rapid addition of water to organic solutions, and rapid addition of organic solutions into water. Several common organic solvents have been used: tetrahydrofuran (THF), dimethylformamide (DMF), dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO). The dialysis method is not reproducible and leads to very large and polydispersed particles (~1µm). In contrast, nanoparticles are formed by the two other methods with a low polydispersity and a size in the 30-10 nm range, depending on the organic solvent used. The particle size increases when the concentration in the organic solvent is decreased. The effect of temperature and length of the hydrophobic block has also been studied. [less ▲]

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See detailAmphiphilic block copolymers of high-molecular-weight poly(ethylene oxide) and either epsilon-caprolactone or gamma-methyl-epsilon-caprolactone: Synthesis and characterization
Vangeyte, Patrick; Jérôme, Robert ULg

in Journal of Polymer Science. Part A, Polymer Chemistry (2004), 42(5), 1132-1142

Ethylene oxide (EO) has been block-polymerized with both epsilon-caprolactone (epsilon-CL) and gamma-methyl-epsilon-caprolactone (MCL) through the combination of the anionic polymerization of EO and the ... [more ▼]

Ethylene oxide (EO) has been block-polymerized with both epsilon-caprolactone (epsilon-CL) and gamma-methyl-epsilon-caprolactone (MCL) through the combination of the anionic polymerization of EO and the ring-opening polymerization (ROP) of epsilon-CL and MCL. omega-Hydroxyl poly(ethylene oxide) has been reacted with triethylaluminum (OH/Al = 1) and converted into a macroinitiator for ROP of epsilon-CL and MCL. In toluene at room temperature, this polymerization leads to a bimodal molecular weight distribution as a result of monomer insertion in only some of the aluminum alkoxide bonds. However, in a more polar solvent (methylene chloride) added with 1 equiv of a Lewis base (pyridine), the expected diblock is formed selectively, and this indicates that aggregation of the active species in toluene is responsible for a macroinitiator efficiency of less than 1. A series of amphiphilic diblock copolymers with poly(epsilon-caprolactone) (semicrystalline) and poly(gamma-methyl-epsilon-caprolactone) (amorphous) as the hydrophobic blocks have been prepared and characterized with size exclusion chromatography, H-1 NMR, IR, and wide-angle X-ray scattering. [less ▲]

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See detailSelf-assembling of poly(-caprolactone)-b-poly(ethylene oxide) diblock copolymers in aqueous solution and at the silica–water interface
Leyh, Bernard ULg; Vangeyte, Patrick; Heinrich, M. et al

in Physica B: Condensed Matter (2004), 350(1-3, suppl. 1), 901-904

Small-angle neutron scattering is used to investigate the self-assembling behaviour of poly( ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers with various block lengths (i) in aqueous solution ... [more ▼]

Small-angle neutron scattering is used to investigate the self-assembling behaviour of poly( ε-caprolactone)-b-poly(ethylene oxide) diblock copolymers with various block lengths (i) in aqueous solution, (ii) in aqueous solution with the addition of sodium dodecyl sulphate (SDS) and (iii) at the silica-water interface. Micelles are observed under our experimental conditions due to the very small critical micellar concentration of these copolymers (0.01 g/l). The poly( ε-caprolactone) core is surrounded by a poly(ethylene oxide) corona. The micellar form factors have been measured at low copolymer concentrations (0.2 wt%) under selected contrast matching conditions. The data have been fitted to various analytical models to extract the micellar core and corona sizes. SDS is shown to induce partial micelle disruption together with an increase of the poly(ethylene oxide) corona extension from 25% (without SDS) to 70% (with SDS) of a completely extended PEOi u chain. Our data at the silica-water interface are compatible with the adsorption of micelles. [less ▲]

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See detailStructure of diblock copolymers in aqueous solution in the presence of a classical surfactant
Vangeyte, Patrick; Leyh, Bernard ULg; Heinrich, M. et al

Poster (2003, May 16)

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