References of "Varshney, Sunil K"
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See detailSelf-assembly of block copolymer complexes in organic solvents
Lefèvre, Nathalie ULg; Fustin, Charles-André; Varshney, Sunil K. et al

in Polymer (2007), 48(8), 2306-2311

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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 detailElectrostatic complexation as a driving force for the self-association of double hydrophilic diblock copolymers in water
Gohy, Jean-François; Mores, Sandrine; Antoun, Sayed et al

Poster (2003, May 16)

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See detailSelf-organization of water-soluble complexes of a poly(2-vinylpyridinium)-block-poly(ethylene oxide) diblock with fluorinated anionic surfactants
Gohy, Jean-François; Mores, Sandrine; Varshney, Sunil K et al

in Macromolecules (2003), 36(8), 2579-2581

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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 detailpH-Dependence of the morphology of micelles formed by poly(2-vinylpyridine)-block-poly(ethylene oxide) copolymers in water
Gohy, Jean-François; Mores, Sandrine; Varshney, Sunil K et al

in e-Polymers (2002), (21), 1-8

The morphology of micelles formed by two poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) copolymers has been studied in phosphate-buffered water by dynamic light scattering and transmission ... [more ▼]

The morphology of micelles formed by two poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) copolymers has been studied in phosphate-buffered water by dynamic light scattering and transmission electron microscopy. Spherical micelles are observed when the P2VP block is the minor component of the diblock copolymer. When P2VP dominates the composition, transition from spheres-to-rods-to-vesicles takes place in a narrow pH range that straddles the pKa of P2VP. This transition is controlled by the degree of protonation of the P2VP blocks. At high pH, the copolymer precipitates from the solution. [less ▲]

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See detailWater-soluble complexes formed by poly(2-vinylpyridinium)-block-poly(ethylene oxide) and poly(sodium methacrylate)-block-poly(ethylene oxide) copolymers
Gohy, Jean-François; Varshney, Sunil K; Jérôme, Robert ULg

in Macromolecules (2001), 34(10), 3361-3366

Formation of interpolyelectrolyte complexes (IPEC) by mixing protonated poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) with neutralized poly(methacrylic acid)-block-poly(ethylene oxide ... [more ▼]

Formation of interpolyelectrolyte complexes (IPEC) by mixing protonated poly(2-vinylpyridine)-block-poly(ethylene oxide) (P2VP-b-PEO) with neutralized poly(methacrylic acid)-block-poly(ethylene oxide) (PMAA-b-PEO) has been investigated in water. It was observed that (i) IPEC are formed in a limited pH range, which is controlled by the degree of ionization of the PMAA and P2VP blocks; (ii) IPEC self-assemble to form the core of monodisperse spherical micelles surrounded by a corona of PEO blocks; (iii) IPEC are salt-sensitive, falling apart above a critical salt concentration; (iv) IPEC are not observed at high pH, but micelles are formed by the P2VP-b-PEO copolymers, which contain an uncharged P2VP core surrounded by a PEO corona; (v) IPEC are not observed at low pH, but the PMAA-b-PEO diblocks aggregate into micelles, the core of which is formed by a hydrogen-bonded complex between PMAA and PEO; and (vi) these PMAA-b-PEO micelles, which are temperature-sensitive, show a complete reorganization of the micellar core above a critical temperature. [less ▲]

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See detailWater-soluble complexes formed by sodium poly(4-styrenesulfonate) and a poly(2-vinylpyridinium)-block-poly(ethyleneoxide) copolymer
Gohy, Jean-François; Varshney, Sunil K; Antoun, Said et al

in Macromolecules (2000), 33(25), 9298-9305

Formation of interpolyelectrolyte complexes (IPEC) between sodium poly(4-styrenesulfonate) (PSSO3Na) and a diblock copolymer consisting of a protonated poly(2-vinylpyridine) (P2VP) block and a neutral ... [more ▼]

Formation of interpolyelectrolyte complexes (IPEC) between sodium poly(4-styrenesulfonate) (PSSO3Na) and a diblock copolymer consisting of a protonated poly(2-vinylpyridine) (P2VP) block and a neutral poly(ethylene oxide) (PEO) one was investigated in water. The main experimental variables were the molecular weight (MW) of the PSSO3Na polyanion, the molar ratio of the cationic and anionic species (i.e., the stoichiometry of the complex), and the pH of the aqueous solution. It was observed that (i) the interpolyelectrolyte complexes self-assemble at least at low pH into the core of monodisperse spherical micelles surrounded by a corona of PEO blocks and possibly of uncomplexed PSSO3Na segments, (ii) their stability depends on the pH in relation to the degree of protonation of the P2VP block, whatever the MW of the PSSO3Na polyanion and the cation/anion stoichiometry, (iii) the complexes are dissociated above a critical pH and are salt-sensitive, falling apart above a critical salt concentration, and (iv) a cooperative mechanism operates, which is completely reversible. [less ▲]

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See detailControl of living anionic polymerization of (meth)acrylates : active complex species, macromolecular engineering and possible scaling-up
Teyssié, Philippe; Bayard, Philippe; Jérôme, Robert ULg et al

in Macromolecular Symposia (1995), 98

Tailored polymerization of acrylic and methacrylic esters, particularly methyl methacrylate (MMA), has been the topic of a frantic research effort during the last decade. It is the purpose of this paper ... [more ▼]

Tailored polymerization of acrylic and methacrylic esters, particularly methyl methacrylate (MMA), has been the topic of a frantic research effort during the last decade. It is the purpose of this paper to present one of the main lines of that quest, and to evaluate its potential versus other new approaches. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 17. Ligated anionic living polymerization of 2-ethylhexyl acrylate as promoted by polydentate lithium alkoxides
Wang, Jin-Shan; Bayard, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1994), 27(18), 4890-4895

Different initiators combined with a new family of mu/sigma dual ligands, i.e., polydentate alkoxides, were used to initiate the anionic polymerization of 2-ethylhexyl acrylate (2EtHA) at low temperatures ... [more ▼]

Different initiators combined with a new family of mu/sigma dual ligands, i.e., polydentate alkoxides, were used to initiate the anionic polymerization of 2-ethylhexyl acrylate (2EtHA) at low temperatures. It has been found that lithium 2(2-methoxyethoxy) ethoxide (LiOEEM) is the most efficient mu/sigma ligand in promoting a living polymerization of that monomer. Although LiOEEM gives rise to a molecularly well-controlled P2EtHA at -78 degrees C in a 9/1 toluene/THF mixture, i.e., quantitative yield, high initiator efficiency (>90%), and narrow molecular weight distribution (M(w)/M(n) down to 1.05), two-step monomer resumption experiments always lead to a bimodal distribution, suggesting that the LiOEEM-complexed P2EtHA anions are not stable. Nevertheless, a perfectly living 2EtHA anionic polymerization process has been obtained at -100 degrees C, keeping other conditions unchanged. In comparison with other types of ligands, such as LiCl and LiOtBu (both mu-ligands) and DB18CE6 and K222 (both sigma-ligands), it has been further demonstrated that the formation of a stable and bulky active complex is at the origin of the anionic living polymerization of 2EtHA, in agreement with our findings in the case of anionic statistical copolymerization of methacrylate and acrylate. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 8. Synthesis and characterization of (meth)acrylic end-functionalized polymers: macromonomers and telechelics
Varshney, Sunil K; Bayard, Philippe; Jacobs, Christian et al

in Macromolecules (1992), 25(21), 5578-5584

Tailor-made poly(tert-butyl acrylate) macromonomers, which are useful building blocks for the synthesis of comb or multiblock copolymers, have been successfully synthesized by deactivation of living PtBA ... [more ▼]

Tailor-made poly(tert-butyl acrylate) macromonomers, which are useful building blocks for the synthesis of comb or multiblock copolymers, have been successfully synthesized by deactivation of living PtBA macroanions with suitable electrophiles bearing either styrene or methacrylic unsaturation. Mono- or bifunctional initiators such as sec-butyllithium or naphthalenyllithium can be used. When these initiators were modified by LiCl as a mu-type ligand, the macroanions which are known to be living were functionalized with high efficiency. Characterization of the various macromonomers was performed using H-1 NMR spectroscopy and SEC. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 6. Synthesis, characterization, and modification of poly(methyl methacrylate)-poly(tert-butyl acrylate) di- and triblock copolymers
Varshney, Sunil K; Jacobs, Christian; Hautekeer, Jean-Paul et al

in Macromolecules (1991), 24(18), 4997-5000

Poly(methyl methacrylate)-b-poly(tert-butyl acrylate) (PMMA-b-PtBA) copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and tert-butyl ... [more ▼]

Poly(methyl methacrylate)-b-poly(tert-butyl acrylate) (PMMA-b-PtBA) copolymers have been successfully synthesized by the sequential anionic polymerization of methyl methacrylate (MMA) and tert-butyl acrylate (tBA) in THF at -78-degrees-C. Although the order of monomer addition makes a difference on the initiation efficiency, it has no significant effect on the final achievement. Mono- and bifunctional initiators based on alkali metals can be used. When the initiators are modified by LiCl as a ligand, the polymerization of each block appears to be living, the molecular weight and composition can be predicted, and the molecular weight distribution is narrow. Size exclusion chromatography supports the absence of homo-PtBA in the PtBA-b-PMMA samples. The PtBA blocks can be quantitatively hydrolyzed into polyacid ones as supported by titration and H-1 NMR analysis. [less ▲]

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See detailAnionic polymerization of acrylic monomers. V. Synthesis, characterization and modification of polystyrene-poly(tert-butyl acrylate) di- and triblock copolymers
Hautekeer, Jean-Paul; Varshney, Sunil K; Fayt, Roger et al

in Macromolecules (1990), 23(17), 3893-3898

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See detailTermination mechanism in the anionic copolymerization of methyl methacrylate and tert-butyl acrylate
Jacobs, Christian; Varshney, Sunil K; Hautekeer, Jean-Paul et al

in Macromolecules (1990), 23(17), 4024-4025

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See detailAnionic polymerization of (meth)acrylic monomers. IV. Effect of lithium salts as ligands on the "living" polymerization of methyl methacrylate using monofunctional initiators
Varshney, Sunil K; Hautekeer, J. P.; Fayt, Roger et al

in Macromolecules (1990), 23

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See detailNew initiator system for the "living" anionic polymerization of tert-alkyl acrylates
Fayt, Roger; Forte, C.; Jacobs, C. et al

in Macromolecules (1987), 20(6), 1442-1444

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