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See detailSynthesis of poly(vinyl acetate)-b-polystyrene and poly(vinyl alcohol)-b-polystyrene copolymers by cobalt-mediated radical polymerization
Bryaskova, Rayna ULg; Willet, Nicolas ULg; Debuigne, Antoine ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (2007), 45(1), 81-89

Well-defined poly(vinyl acetate) macroinitiators, with the chains thus end-capped by a cobalt complex, were synthesized by cobalt-mediated radical polymerization and used to initiate styrene ... [more ▼]

Well-defined poly(vinyl acetate) macroinitiators, with the chains thus end-capped by a cobalt complex, were synthesized by cobalt-mediated radical polymerization and used to initiate styrene polymerization at 30 degrees C. Although the polymerization of the second block was not controlled, poly(vinyl acetate)-b-polystyrene copolymers were successfully prepared and converted into amphiphilic poly(vinyl alcohol)-b-polystyrene copolymers by the methanolysis of the ester functions of the poly(vinyl acetate) block. These poly(vinyl alcohol)-b-polystyrene copolymers self-associated in water with the formation of nanocups, at least when the poly(vinyl alcohol) content was low enough. [less ▲]

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See detailpH-responsive micelles in dilute and gel-like media
Willet, Nicolas ULg; Leyh, Bernard ULg; Gohy, Jean-François et al

Conference (2006, June)

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See detailpH-Responsive diblock copolymers prepared by the dual initiator strategy
Bernaerts, Katrien V.; Willet, Nicolas ULg; Van Camp, Wim et al

in Macromolecules (2006), 39(11), 3760-3769

Diblock copolymers poly(tetrahydrofuran-b-tert-butyl acrylate) (PTHF-b-PtBA) and poly(tetrahydrofuranb- 1-ethoxyethyl acrylate) (PTHF-b-PEEA) were successfully synthesized by the dual initiator 4 ... [more ▼]

Diblock copolymers poly(tetrahydrofuran-b-tert-butyl acrylate) (PTHF-b-PtBA) and poly(tetrahydrofuranb- 1-ethoxyethyl acrylate) (PTHF-b-PEEA) were successfully synthesized by the dual initiator 4-hydroxybutyl-2- bromoisobutyrate (HBBIB). The isobutyrate and alcohol function of HBBIB were used for the atom transfer radical polymerization of tBA ( or EEA) and the living cationic ring-opening polymerization of THF, respectively. Hydrolysis or thermolysis of the aforementioned diblock copolymers results in amphiphilic pH-responsive copolymers PTHF-b-poly( acrylic acid) ( PTHF-b-PAA). Matrix-assisted laser desorption/ ionization time-of-flight (MALDI-TOF) and nuclear magnetic resonance spectroscopy (H-1 NMR) were used to analyze the PTHF macroinitiator, while clear evidence for the formation of well-defined block copolymer structures was obtained by 1H NMR, gel permeation chromatography (GPC), and infrared spectroscopy (FT-IR). The amorphous PtBA block in PTHF-b-PtBA resulted in a decrease of the crystallinity and the melting point of PTHF, as shown by differential scanning calorimetry (DSC). Self-assembly of PTHF-b-PAA copolymers in water into aggregates and micelles when exposed to specific pH values was confirmed by dynamic light scattering, infrared, and NMR spectroscopies. [less ▲]

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See detailDependence of the structure of core-shell-corona micelles on the composition of water/toluene mixtures
Lei, Liangcai; Gohy, Jean-François; Willet, Nicolas ULg et al

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 ▲]

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See detailSynthesis of poly(vinyl acetate) and poly(vinyl alcohol) containing block copolymers by combination of cobalt-mediated radical polymerization and ATRP
Debuigne, Antoine ULg; Caille, Jean-Raphaël; Willet, Nicolas ULg et al

in Macromolecules (2005), 38(23), 9488-9496

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an ... [more ▼]

Poly(vinyl acetate) (PVAc) chains of a low polydispersity (Mw/Mn similar to 1.1-1.2) have been prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc). They have been end-capped by an activated bromide by addition of an alpha-bromoester or an alpha-bromoketone containing nitroxide and converted into effective macroinitiators for the atom transfer radical polymerization of styrene (Sty), ethyl acrylate, and methyl methacrylate. Because each block is formed by a controlled process, well-defined PVAc containing diblock copolymers are easily prepared. The PVAc-b-PS copolymers synthesized from alpha-bromoketone end-capped PVAc can be converted into well-defined poly(vinyl alcohol)-b-polystyrene amphiphiles by methanolysis of the poly(vinyl acetate) block. Self-association of an amphiphilic poly(vinyl alcohol)(3500)-b-polystyrene(16 600) in a (4/1) water/tetrahydrofuran mixture results in the formation of vesicles as observed by transmission electron microscopy. [less ▲]

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See detailCore-shell-corona micelles: focus on the pH-responsive shell
Willet, Nicolas ULg; Gohy, Jean-François; Jérôme, Robert ULg

Conference (2005, October)

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See detailABC triblock copolymers for pH sensitive micelles
Willet, Nicolas ULg; Gohy, Jean-François; Varshney, Sunil et al

Poster (2005, June 01)

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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 detailSegregation of coronal chains in micelles formed by supramolecular interactions
Gohy, Jean-François; Khousakoun, Eric; Willet, Nicolas ULg et al

in Macromolecular Rapid Communications (2004), 25(17), 1536-1539

Spherical micelles have been formed by mixing, in DMF, a poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-block-P2VP-block-PEO) triblock copolymer with either poly(acrylic acid ... [more ▼]

Spherical micelles have been formed by mixing, in DMF, a poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-block-P2VP-block-PEO) triblock copolymer with either poly(acrylic acid) (PAA) or a tapered triblock copolymer consisting of a PAA central block and PEO macromonomer-based outer blocks. Noncovalent interactions between PAA and P2VP result in the micellar core while the outer corona contains both PS and PEO chains. Segregation of the coronal chains is observed when the tapered copolymer is used. [less ▲]

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See detailMorphology of core-shell-corona aqueous micelles: II. Addition of core-forming homopolymer
Lei, Liangcai C; Gohy, Jean-François; Willet, Nicolas ULg et al

in Polymer (2004), 45(13), 4375-4381

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

The poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) triblock copolymer PS200-b-P2VP(140)-b-PEO590, where the subscripts refer to the number average degrees of polymerization, forms spherical micelles in water, that consist of a PS core, a pH-responsive P2VP shell and a PEO corona. This triblock has been added with homo-PS before micellization in order to increase the volume fraction of the core-forming block. The length of the added homo-PS has been varied with respect to the length of the PS core-forming block: much shorter, much longer and approximately the same. The structure of the micelles has been investigated by transmission electron microscopy, static and dynamic light scattering. Homo-PS phase separates whenever its length is larger than the one of the PS core-forming chains; otherwise this phenomenon occurs beyond a critical concentration that depends on molecular weight. The addition of homo-PS has no influence on the morphology of the micelles and on the characteristic size of both the PS core and the P2VP shell, although the hydrodynamic diameter of the micelles is decreased. Substitution of styrene for homopolystyrene results in transition from a spherical to a dominant rod-like morphology. (C) 2004 Published by Elsevier Ltd. [less ▲]

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See detailDesign of nanoobjects endowed with specific properties
Willet, Nicolas ULg; Qiu, Hongjin; Rieger, Jutta ULg et al

Conference (2004, March)

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See detailTuning of the morphology of core-shell-corona micelles in water. I. Transition from sphere to cylinder
Lei, Liangcai; Gohy, Jean-François; Willet, Nicolas ULg et al

in Macromolecules (2004), 37(3), 1089-1094

Poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) ABC triblock copolymers commonly form core-shell-corona (CSC) micelles in water. These micelles consist of a PS ... [more ▼]

Poly(styrene)-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) (PS-b-P2VP-b-PEO) ABC triblock copolymers commonly form core-shell-corona (CSC) micelles in water. These micelles consist of a PS spherical core, a P2VP shell, and a PEO corona. However, when the micelles are formed in the presence of a solvent selective for the PS block (benzene), the micellar morphology exhibits a sphere-to-rod transition, as result of the increased volume fraction of the core-forming blocks. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) confirm that a PS rod-like core is surrounded by a P2VP shell and an external PEO corona. Nevertheless, the rod-like micelles coexist with spherical micelles that should be thermodynamically less stable, because of a higher stretching of the PS chains in the core. The P2VP chains are also in a stretched conformation, whatever the pH. The P2VP shell has been used as nanoreactor for the production of gold nanoparticles. [less ▲]

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See detailElectrografting of polymers onto AFM tips: A novel approach for chemical force microscopy and force spectroscopy
Jérôme, Christine ULg; Willet, Nicolas ULg; Jérôme, Robert ULg et al

in Chemphyschem : A European Journal of Chemical Physics and Physical Chemistry (2004), 5(1), 147-149

Polymer-modified AFM tips have been prepared through an easily implemented and versatile electrochemical method (see graphic). The authors describe the electropolymerization process of acrylic-based ... [more ▼]

Polymer-modified AFM tips have been prepared through an easily implemented and versatile electrochemical method (see graphic). The authors describe the electropolymerization process of acrylic-based monomers onto gold-coated tips (see graphic) and show force curves obtained during approach-retraction cycles between the modified tips and a bare silicon surface. This direct chemical grafting creates new possibilities for single-molecule force spectroscopy. [less ▲]

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See detailFunctionalization of AFM tips by electrografting
Jérôme, Christine ULg; Willet, Nicolas ULg; Gabriel, Sabine ULg et al

Poster (2003, May 16)

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See detailFrom spherical to cyclindrical micelles formed by polystyrene-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) copolymer in water
Lei, Liangcai; Gohy, Jean-François; Willet, Nicolas ULg et al

Poster (2003, May 16)

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See detailStimuli-responsive core-shell-corona micelles in water
Willet, Nicolas ULg; Gohy, Jean-François; Varshney, Sunil et al

Poster (2003, May 16)

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See detailStimuli-responsive core-shell-corona micelles in water
Willet, Nicolas ULg; Lei, Liangcai; Gohy, Jean-François et al

Conference (2003, May)

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See detailpH Dependence of the morphology of aqueous micelles formed by polystyrene-block-poly(2-vinylpyridine)-block-poly(ethylene oxide) copolymers
Gohy, Jean-François; Willet, Nicolas ULg; Varshney, Sunil K et al

in e-Polymers (2002), (35), 1-10

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 ... [more ▼]

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. [less ▲]

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See detailCore-Shell-Corona micelles with a responsive shell
Willet, Nicolas ULg; Gohy, Jean-François; Jérôme, Robert ULg

Conference (2002, April 12)

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