References of "Jérôme, Robert"
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See detailA new family of "ligated" anionic initiators for the "living" polymerization of (meth)acrylic esters
Bayard, Philippe; Jérôme, Robert ULg; Teyssié, Philippe et al

in Polymer Bulletin (1994), 32(4), 381-385

A new family of ligands (dual sigma - pi ligand), i.e. chelating lithium alkoxides, Li-O-(CH2-CH2O)nCH3, is shown to be very effective in promoting the living anionic Polymerization of methacrylic and ... [more ▼]

A new family of ligands (dual sigma - pi ligand), i.e. chelating lithium alkoxides, Li-O-(CH2-CH2O)nCH3, is shown to be very effective in promoting the living anionic Polymerization of methacrylic and acrylic esters, including a number of primary alkyl acrylates such as n-butyl acrylate and 2-ethylhexylacrylate. [less ▲]

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See detailSelective localization of carbon black in immiscible polymer blends : a useful tool to design electrical conductive composites
Gubbels, Frédéric; Jérôme, Robert ULg; Teyssié, Philippe et al

in Macromolecules (1994), 27(7), 1972-1974

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See detailAnionic polymerization of acrylic monomers. 13. Carbon-13 NMR characterization of the mixed complexation of methyl α-lithioisobutyrate by lithium tert-butyoxide in tetrahydrofuran
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1994), 27(24), 1691-1696

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for ... [more ▼]

The mixed complexation of methyl alpha-lithioisobutyrate(MIBLi)(a monomeric model structurally corresponding to the living end of PMMA-Li+) with lithium tert-butoxide (LiOtBu) in THF has been studied for the first time by using C-13 NMR spectroscopy. It is shown that LiOtBu, like LiCl, is very effective in coordinating with MIBLi tetramer in THF, incrementally replacing MIBLi with the formation of other tetrameric complexes, MIBxLi4(OtBu)4-x (x = 1-3). Complextion of MIBLi by LiOtBu induces a shielding C-13 shift of the MIBLi C(alpha) resonance, which might suggest that lithium cations associated with the electron-rich ligands, i.e., LiOtBu, can also form weaker bonds with the carbonyl oxygen of MIBLi (i.e., mu-type complexes), thereby decreasing the localization of the negative charge on that latter atom. In comparison with LiCl, one of the most significant features is that only one single type of species results from mixed complexation of MIBLi and LiCl at LiCl/MIBLi = 1, 2, and greater-than-or-equal-to 3, respectively, at low temperature, whereas several LiOtBu-complexed species may coexist, whatever the LiOtBu/MIBLi ratio; furthermore, their exchange is found to be very slow at a temperature as high as 0-degrees-C. Tentatively, this striking feature may explain nicely the large difference in molecular weight distribution of poly(meth)acrylates anionically prepared in the presence of LiOtBu and LiCl, respectively. [less ▲]

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See detailSalt-free polyelectrolyte behavior of polystyrene-based telechelic ionomers in a polar solvent. 1. Viscosity and low-angle light scattering studies
Wu, Jhi-Li; Wang, Yu-Min; Hara, Masanori et al

in Macromolecules (1994), 27(5), 1195-1200

Some characteristic behavior, typically observed for salt-free polyelectrolytes in water, was observed for the first time for polystyrene (PS)-based telechelic ionomers, which have ionic groups located ... [more ▼]

Some characteristic behavior, typically observed for salt-free polyelectrolytes in water, was observed for the first time for polystyrene (PS)-based telechelic ionomers, which have ionic groups located only at the chain ends, when dissolved in a polar solvent, dimethylformamide (DMF). The characteristic behavior observed by both viscosity and low-angle light scattering measurements for the telechelic ionomers, especially that of the monofunctional ionomer, demonstrates an important role of intermolecular electrostatic interactions in causing the characteristic behavior of telechelic ionomers. The behavior observed in our experiments can best be described by the following picture: each ionomer molecule with a coil conformation, very close to that of polystyrene of the same molecular weight, is separated from yet strongly interacts with other ionomer molecules; and these strong intermolecular electrostatic interactions cause a marked upturn in reduced viscosity and a reduction in scattered intensity. [less ▲]

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See detailEnzyme Immobilization in Nanoparticles produced by Inverse Microemulsion Polymerization
Daubresse, Catherine; Grandfils, Christian ULg; Jérôme, Robert ULg et al

in Journal of Colloid & Interface Science (1994), 168

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See detailEffect of the emulsion stability on the morphology and porosity of semicrystalline poly-L-lactide micriparticles prepared by w/o/w double emulsion-evaporation
Schugens, Ch; Laruelle, N; Nihant, N et al

in Journal of Controlled Release (1994), 32

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See detailPolylactide Microparticules Prepared by Double Emulsion/Evaporation Technique. I. Effect of Primary Emulsion Stability
Nihant; Schugens, Chantal; Grandfils, Christian ULg et al

in Pharmaceutical Research (1994), 11(10), 1479-1484

The process of microencapsulation of proteins by double emulsion-evaporation in a matrix of polylactide (PLA) can be divided into three successive steps: first, an aqueous solution of the active compound ... [more ▼]

The process of microencapsulation of proteins by double emulsion-evaporation in a matrix of polylactide (PLA) can be divided into three successive steps: first, an aqueous solution of the active compound is emulsified into an organic solution of the hydrophobic coating polymer; second, this primary water-in-oil (w/o) is dispersed in water with formation of a double water-oil-water emulsion (w/o/w), third, the organic solvent is removed with formation of solid microparticles. This paper focuses of the effect of primary emulsion stability on the morphology and properties of polylactide microparticles loaded with bovine serum albumin (BSA) used as model drug. [less ▲]

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See detailMicroencapsulation by Coacervation of Poly(lactide-co-glycolide). III. Characterization of the Final Microspheres
Nihant, Nicole; Stassen, Sophie; Grandfils, Christian ULg et al

in Polymer International (1994), 34

This paper deals with protein microencapsulation by coacervation of poly(lactide-co-glycolide) solutions in CH2Cl2 induced by the addition of silicone oils of various viscosities. This coating technique ... [more ▼]

This paper deals with protein microencapsulation by coacervation of poly(lactide-co-glycolide) solutions in CH2Cl2 induced by the addition of silicone oils of various viscosities. This coating technique proceeds along three steps: phase separation of the coating polyester, adsorption of the coacervate droplets around the protein phase, and hardening of microparticules. Size distribution, surface morphology and internal porosity of the final microspheres clearly depend on the main characteristics of the coacervate, particularly the viscosity, in a direct connection with the CH2Cl2 content. Indeed, the whole porosity (which may be as high as 80%), average pore size and broadness of pore size distribution decrease as the coacervate is more viscous. Hardening of the coacervate droplets is thus so fast that the organic solvent is entrapped within the polymer matrix and predetermines the internal porosity. Finally, size distribution of microspheres is bimodal in a clear relation with the coacervate viscosity. A less viscous coacervate favours smaller microspheres (within the 7-90 µm range), contaminated with a minor population of microparticles below 4 µm. [less ▲]

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See detailMicroencapsulation by coacervation of poly(lactide-co-glycolide): Physico-chemical characteristics of the phase separation process
Stassen, S; Nihant, Nicole; Martin, Véronique et al

in Polymer (1994), 35(4), 777-785

This paper describes the phase separation of different lactide and glycolide copolyester solutions, induced by the addition of silicone oil in order to promote protein microencapsulation. The phase ... [more ▼]

This paper describes the phase separation of different lactide and glycolide copolyester solutions, induced by the addition of silicone oil in order to promote protein microencapsulation. The phase diagrams of the ternary CH2Cl2-copolyester-silicone oil systems were established in relation to the composition of the copolyester and the viscosity, i.e. the molecular weight, of the silicone oil. The phase-separated systems were characterized in terms of weight, volume, composition and viscosity of the coacervation agent (silicone oil) on the characteristics of the phase-separated system is discussed. [less ▲]

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See detailAnionic polymerization of acrylic monomers. 11 NMR investigation of the mixed complexation of methyl α-lithioisobutyrate and lithium chloride
Wang, Jin-Shan; Warin, R.; Jérôme, Robert ULg et al

in Macromolecules (1993), 26

Solutions of methyl α-lithioisobutyrate (MIBLi) in THF added with various amounts of lithium chloride (LiCl) have been analyzed by Li-7 NMR spectroscopy in a wide range of temperatures. Although below ca ... [more ▼]

Solutions of methyl α-lithioisobutyrate (MIBLi) in THF added with various amounts of lithium chloride (LiCl) have been analyzed by Li-7 NMR spectroscopy in a wide range of temperatures. Although below ca. 205 K tetramers of MIBLi have been reported to be in equilibrium with dimers, 1/1 and 2/1 LiCl/MIBLi mixed complexes instantaneously form upon the addition of 1 and 2 mol equiv of LiCl, respectively. Further addition of LiCl more likely promotes the formation of a less stable 3/1 complex. Both 1/1 and 2/1 adducts are stable between -80-degrees-C and at least +12-degrees-C. From C-13 NMR spectroscopy, it appears that the addition of an equimolar amount of LiCl to the MIBLi solution in THF is at the origin of a ca. 7.0 ppm upfield shift of the metalated α-carbon compared to the tetrameric MIBLi species and a ca. 1.0 ppm downfield shift with respect to the dimeric MIBLi. However, the charge distribution over the carbanion does not change anymore when the amount of LiCl exceeds 1 mol equiv. In contrast to nonligated MEBLi, the OR group has a considerable rotational freedom in LiCl-modified MIBLi. A comparison of the structure and dynamics of the LiCl-modified MIBLi species in THF at 197 K with the characteristic features of the anionic polymerization of MMA under the same conditions suggests that the formation of one type of LiCl-complexed species has a decisive effect on the control of the living polymerization of MMA. This conclusion is in agreement with a kinetic study carried out by Muller for the same system. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 14. A 13C and 27Al NMR study of the effect of γ-butyrolactone on the structure of aluminum isopropoxide in toluene
Ropson, Nathalie; Dubois, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1993), 26(24), 6378-6385

Solutions of Al isopropoxide in toluene have been investigated by C-13 and Al-27 NMR spectroscopy. Since Al(OiPr)3 is currently used as an initiator for the living polymerization of epsilon-caprolactone ... [more ▼]

Solutions of Al isopropoxide in toluene have been investigated by C-13 and Al-27 NMR spectroscopy. Since Al(OiPr)3 is currently used as an initiator for the living polymerization of epsilon-caprolactone, special attention has been paid to the effect of the monomer on the coordinative structure of Al(OiPr3) in toluene. Gamma-butyrolactone (BL) has been chosen as a nonpolymerizable model, representative of epsilon-caprolactone. The NMR spectra have been recorded at various concentrations of gamma-butyrolactone and temperatures. As a rule, Al(OiPr)3 is coordinatively aggregated in toluene in such a way that tetrameric and trimeric species are in equilibrium. Upon the addition of BL, this equilibrium is shifted toward the formation of an octahedric [Al(OiPr)3.3BL] mixed tetramer coexisting with [Al(OiPr)3]4 tetramers, the external tetrahedric Al atoms of which are coordinated with extra BL molecules. In the presence of a large excess of BL, only the mixed tetramer persists, which suggests that the single [Al(OiPr)3.3M] species would be the actual initiator for the ring-opening polymerization of cyclic monomers M, such as epsilon-caprolactone, lactides, glycolide, and cyclic anhydrides. [less ▲]

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See detailSurface concentration of chain ends in polystyrene determined by static secondary ion mass spectroscopy
Affrossman, S.; Hartshorne, M.; Jérôme, Robert ULg et al

in Macromolecules (1993), 26(23), 6251-6254

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See detailAnionic polymerization of (meth)acrylic monomers. 12. Efect of lithium chloride on the stereochemistry on the anionic polymerization of methyl methacrylate in THF and in a 9/1 toluene/THF mixture
Wang, Jin-Shan; Jérôme, Robert ULg; Warin, Roger et al

in Macromolecules (1993), 26(22), 5984-5990

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been ... [more ▼]

The effect of LiCl on the stereochemistry of the anionic polymerization of methyl methacrylate in the presence of a lithium counterion at -78-degrees-C in THF and in a 9/1 toluene/THF mixture, has been studied by C-13 and H-1 NMR spectroscopy. It has been found that LiCl has an important effect on the E/Z ratio of the living chain ends in THF, in contrast to the main-chain tacticity. In contrast, LiCl has a significant influence on the stereoregularity of the anionic polymerization of MMA in a 9/1 toluene/THF mixture. When the LiCl/initiator molar ratio is increased, the syndiotactic placements (rr) are favored at the expense of the isotactic ones (mm). This effect can be accounted for by a multistate propagating mechanism controlled by association/complexation equilibria among associated, nonassociated, and LiCl-complexed species. These association/complexation equilbria, which were originally proposed by Muller, appear to have a decisive effect not only on the livingness (molecular weight distribution (MWD)) but also on the stereochemistry of the anionic polymerization of MMA in a 9/1 toluene/THF mixture at -78-degrees-C, confirming the involvement of the ligand in propagation control. [less ▲]

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See detailEnd-attaching copolymer adsorption: kinetics and effects of chain architecture
Dogan, J. R.; Stamm, Manfred; Toprakcioglu, C. et al

in Macromolecules (1993), 26(20), 5321-5330

In this study we report on the adsorption behavior of end-attaching triblock and diblock copolymers. The triblock copolymers consist of relatively short PEO end blocks and a much longer PS middle block or ... [more ▼]

In this study we report on the adsorption behavior of end-attaching triblock and diblock copolymers. The triblock copolymers consist of relatively short PEO end blocks and a much longer PS middle block or, in one case, of zwitterionic end groups with a PS middle block. The diblock materials consist of a PEO block of fixed length and varying polystyrene lengths. A silicon wafer with an oxide layer is used as the surface, and adsorption takes place from toluene; only the end groups adsorb, leaving the polystyrene block dangling in solution. We find that diblock copolymers which range from symmetric to moderately symmetric obey the scaling law for the surface coverage which was proposed in the theory of Marques and Joanny (i.e., sigma is-proportional-to 1/N(A), where N(A) is the number of segments in the adsorbing block). However, we find that for triblock copolymers of comparable asymmetry the surface coverage scales according to the relationship sigma is-proportional-to 1/beta2, where beta is the ratio of the size of the nonadsorbing block to that of the adsorbing block. This implies that moderately symmetric triblock copolymers behave like highly asymmetric diblock copolymers; the adsorption behavior is dominated by the nonadsorbing block size. Our experiments demonstrate the observation of extremely long-lived nonequilibrium states. On the basis of these observations we propose a simplified version of a recent theory of adsorption which is capable of qualitatively describing much of the experimentally observed phenomena. [less ▲]

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See detailSurface composition of poly(styrene-d8-styrene) random copolymers studied by static secondary ion mass spectroscopy
Affrossman, S.; Hartshorne, M.; Jérôme, Robert ULg et al

in Macromolecules (1993), 26(20), 5400-5404

The surface compositions of a series of random copolymers of styrene and deuteriostyrene have been determined by SIMS. The mechanism of fragmentation during the SIMS process is examined, and the ... [more ▼]

The surface compositions of a series of random copolymers of styrene and deuteriostyrene have been determined by SIMS. The mechanism of fragmentation during the SIMS process is examined, and the contribution from naturally occurring isotopes is evaluated. The data are shown to fit a model of a completely random copolymer system if they are corrected for the effects of impurities introduced in the syntheses and for the contribution from C-13. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 12. Study of the depolymerizatin reactions of poly(ε-caprolactone with functional aluminum alkoxide end groups
Dubois, Philippe; Barakat, Ibrahim; Jérôme, Robert ULg et al

in Macromolecules (1993), 26(17), 4407-4412

Ring-opening polymerization of epsilon-caprolactone has been initiated with functional aluminum alkoxides in toluene at 25-degrees-C. Degradation of ''living'' polyester chains by transesterification ... [more ▼]

Ring-opening polymerization of epsilon-caprolactone has been initiated with functional aluminum alkoxides in toluene at 25-degrees-C. Degradation of ''living'' polyester chains by transesterification reactions has been studied in relation to temperature, solvent polarity, average molecular weight, and structure of the initiator, i.e., the nature of the functional group and the number of alkoxides per Al atom. Degradation products, particularly cyclic oligomers, have been isolated by supercritical fluid extraction (SFE) and characterized by GC-MS. The effect of Lewis bases on transesterification reactions has been investigated and discussed in reference to the ''coordination-insertion'' mechanism. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 11. Synthesis and use of alkylaluminium dialkoxides and dithiolates as promoters of hydroxy telechelic poly(epsilon-capprolactone) and alph,omega-dihydroxy triblock copolymers containing outer polyester blocks
Dubois, Philippe; Degée, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1993), 26(11), 2730-2735

Diethylaluminum dialkoxides (Et2AlOXOAlEt2, where X is either an aliphatic radical or a polymer chain) and related dithiolates have been investigated as potential initiators for the ring-opening ... [more ▼]

Diethylaluminum dialkoxides (Et2AlOXOAlEt2, where X is either an aliphatic radical or a polymer chain) and related dithiolates have been investigated as potential initiators for the ring-opening polymerization of ε-caprolactone. Hydroxy telechelic poly(ε-caprolactone) and alpha,omega-dihydroxypoly(ε-caprolactone-b-X-b-ε-caprolactone) have been accordingly prepared and characterized. A hydroxy group is selectively attached at both ends as demonstrated by IR and H-1 NMR spectroscopies and confirmed by titration of the derivatized alpha,omega-dicarboxylic acid (co)polymers. Polymerization of epsilon-caprolactone is living and yields linear polyester chains of a predictable molecular weight and of quite a narrow molecular weight distribution. [less ▲]

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