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See detailLiving (co)polymerization of adipic anhydride and selective end functionalization of the parent polymer
Ropson, Nathalie; Dubois, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1992), 25(14), 3820-3824

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See detailMacromolecular engineering of polylactones and polylactides. 7. Structural analysis of copolyesters of epsilon-caprolactone and L- of D,L-lactide initated by Al(OiPr)3
Vanhoorne, Pierre; Dubois, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1992), 25(1), 37-44

Copolymerization of mixtures of epsilon-caprolactone (epsilon-CL) and D,L- or L-lactide has been initiated by aluminum isopropoxide. On the basis of the monomer reactivity ratios and assuming that no side ... [more ▼]

Copolymerization of mixtures of epsilon-caprolactone (epsilon-CL) and D,L- or L-lactide has been initiated by aluminum isopropoxide. On the basis of the monomer reactivity ratios and assuming that no side reaction occurs, tapered copolymers should be formed particularly when D,L-lactide is the comonomer rather than L-lactide. The sequential distribution of the comonomers has been analyzed by an original method based on the quantitative measurement of the carbonyl C-13 signals. Comparison of the experimental and the theoretical distributions clearly shows that transesterification reactions occur during copolymerization through both intra- and intermolecular mechanisms. Gel permeation chromatography and differential scanning calorimetry data support that conclusion. The D,L-lactide-based copolymers have however a more blocky structure than those containing L-lactide, and they are also less sensitive to transesterification reactions. [less ▲]

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See detailDielectric properties of a model cationic ionomer
Yano, S.; Tadano, K.; Jérôme, Robert ULg

in Macromolecules (1991), 24(24), 6439-6442

An alpha,omega-bis(dimethylamino)polyisoprene (M(n)BAR = 5000) has been quaternized by alpha,alpha'-dibromo-p-xylene with formation of a model cationic ionomer. Dielectric spectroscopy has shown an alpha ... [more ▼]

An alpha,omega-bis(dimethylamino)polyisoprene (M(n)BAR = 5000) has been quaternized by alpha,alpha'-dibromo-p-xylene with formation of a model cationic ionomer. Dielectric spectroscopy has shown an alpha-relaxation which corresponds to the micro-Brownian motion of chain segments directly attached to the quaternary ammonium dipoles. A shoulder on the low-temperature side of the alpha-relaxation has been assigned to the contribution of the polymer segments, the mobility of which is not restricted by the multiplets. That situation is in full agreement with the multiplet-cluster concept recently revisited by Eisenberg et al. [less ▲]

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See detailLiving polymerization and selective end functionalization of ε-caprolactone using zinc alkoxides as initiators
Barakat, Ibrahim; Dubois, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1991), 24

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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 detailMacromolecular engineering of polylactones and polylactides. 5. Synthesis and characterization of diblock copolymers based on poly-ε-caprolactone and poly(L,L or D,L)lactide by aluminum alkoxides
Jacobs, C.; Dubois, Philippe; Jérôme, Robert ULg et al

in Macromolecules (1991), 24(11), 3027-3034

Aluminum isopropoxide is known to be an effective initiator for the ring-opening polymerization of lactides (D,L and L,L) and epsilon-caprolactone (epsilon-CL). For a question of mutual reactivity, the ... [more ▼]

Aluminum isopropoxide is known to be an effective initiator for the ring-opening polymerization of lactides (D,L and L,L) and epsilon-caprolactone (epsilon-CL). For a question of mutual reactivity, the sequential polymerization of these two comonomers can only be achieved when epsilon-CL is first polymerized followed by the lactide. Formation of a large amount of homo PLA is however observed and has been attributed to a great difference in the mean degree of association of aluminum alkoxides in toluene in the presence of epsilon-CL and LA. In toluene, the mean number (n) of active sites per Al(O(i)Pr)3 molecule jumps from 1 to 3 when epsilon-CL is substituted by LA. The addition of a small amount of an alcohol, like 2-propanol, is effective in preventing the aluminum alkoxide from associating, and n is then 3 whatever the monomer used. 2-Propanol participates in the polymerization of epsilon-CL and LA as supported by a decrease in the molecular weight of the final polymer in relation to the molar amount of added alcohol. This means that the alcohol molecules are rapidly exchanged with the alkoxide groups on Al. Under such conditions, the formation of pure diblock copolymers P(epsilon-CL-b-LA) is reported. Another successful strategy for the synthesis of the diblock copolymer consists in using an Al derivative that bears only one alkoxide group to initiate the polymerization of the two cyclic esters. In this regard, a diethylaluminum alkoxide is of great value, particularly the ethoxide one. A third, conceptually similar, approach to the synthesis of P(epsilon-CL-b-LA) copolymers relates to the reaction of a performed hydroxy-terminated PCL with triethylaluminum and the use of that macroinitiator in the ring-opening polymerization of the lactide. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 4. Mechanism and kinetics of lactide homopolymerization by aluminum isopropoxide
Dubois, Philippe; Jacobs, R.; Jérôme, Robert ULg et al

in Macromolecules (1991), 24(9), 2266-2270

Aluminum isopropoxide is an effective initiator for the polymerization of lactides in toluene at 70-degrees-C. The ring-opening polymerization proceeds through a "coordination-insertion" mechanism and ... [more ▼]

Aluminum isopropoxide is an effective initiator for the polymerization of lactides in toluene at 70-degrees-C. The ring-opening polymerization proceeds through a "coordination-insertion" mechanism and selective rupture of the acyl oxygen bond of the monomer. A kinetic study has shown that the polymerization is first order in both the monomer and initiator. The polymerization is typically "living" until a molecular weight of ca. 90 000 is reached. At higher temperatures (100-degrees-C), inter- and intramolecular transesterification reactions are responsible for a limitation in the molecular weight of the growing chains. In toluene, at 70-degrees-C, each alkoxide of the aluminum isopropoxide participates in the polymerization. Any molecular weight below 90 000 can accordingly be predicted on the basis of the monomer/Al molar ratio, and the polydispersity is rather narrow (1.1-1.4). [less ▲]

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See detailMacromolecular Engineering of polylactones and polylactides. 3. Synthesis, characterization and applications of poly(ε-caprolactone) macromonomers
Dubois, Philippe; Jérôme, Robert ULg; Teyssié, Philippe

in Macromolecules (1991), 24(5), 977-981

Well-defined omega-methacryloylpoly(epsilon-caprolactone) (or PCL) macromonomers have been prepared by using an aluminum alkoxide that bears a methacrylic double bond. The initiator results from the ... [more ▼]

Well-defined omega-methacryloylpoly(epsilon-caprolactone) (or PCL) macromonomers have been prepared by using an aluminum alkoxide that bears a methacrylic double bond. The initiator results from the equimolar reaction of triethylaluminum with 2-hydroxyethyl methacrylate (HEMA). The coordination-insertion type of polymerization is living and yields exclusively linear macromonomers of a predictable molecular weight with a narrow molecular weight distribution. IR and H-1 NMR studies show that the methacryloyl group associated with the active alkoxy group of the initiator is selectively attached to one chain end. Should the living polymerization be terminated by methacryloyl chloride, and a alpha,omega-dimethacryloyl-PCL, i.e. a alpha,omega-macromonomer is obtained. PCL macromonomers and HEMA are easily copolymerized in the presence of AIBN, resulting in a hydrophilic poly(HEMA) backbone grafted with hydrophobic PCL subchains. [less ▲]

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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 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 detailViscoelastic properties of telechelic ionomers. I. Complexed α,ω-diamino polydienes
Charlier, Pascal; Jérôme, Robert ULg; Teyssié, Philippe et al

in Macromolecules (1990), 23(13), 3313-3321

Complexation of the end groups of amino telechelic polydienes strongly affects the viscoelastic behavior. This is shown in the thermal dependence of the isochronous torsion modulus of a liquid ... [more ▼]

Complexation of the end groups of amino telechelic polydienes strongly affects the viscoelastic behavior. This is shown in the thermal dependence of the isochronous torsion modulus of a liquid polybutadiene selectively end-capped by a piperazine unit at both extremities. A rubbery plateau emerges when the telechelic polymer is coordinated to copper(I1) or iron(II1) chlorides. The rubbery plateau extends over a temperature range that depends on the molar ratio of the transition metal to the amine end group. Similar observations have been reported when the dynamic mechanical properties of an a,w-bis(dimethylamino) telechelic polyisoprene have been investigated over the full range of temperature from the glassy plateau to the viscous flow. Upon complexation of the end groups, a rubberlike plateau is observed, which does not exist for the uncomplexed polymer. Furthermore, a secondary relaxation, attributed to the aggregation of the complexed amine end groups, occurs above Tg. The temperature at which the maximum of this relaxation is observed and the distribution of the relaxation times depend on the metal to amine endgroup molar ratio. At a ratio of 1, FeC13 endows the chain network with higher cross-link density than CuC12 does. However, at the same time the temperature width of the rubbery plateau is much shorter for the former than for the latter polymer, indicating a relative thermal instability of the Fe-amine complexes. [less ▲]

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See detailEffect of ionic aggregation on ionomer chain dimensions. 1. Telechelic polystyrenes
Register, Richard A; Cooper, Stuart L; Thiyagarajan, Pappannan et al

in Macromolecules (1990), 23(11), 2978-2983

Carboxy-telechelic polystyrenes with degrees of polymerization of ca. 70 were examined by small-angle neutron scattering in the Na+ ionomer and methyl ester forms to ascertain the effect of ionic ... [more ▼]

Carboxy-telechelic polystyrenes with degrees of polymerization of ca. 70 were examined by small-angle neutron scattering in the Na+ ionomer and methyl ester forms to ascertain the effect of ionic aggregation on the chain dimensions. The ionomers contain ionic aggregates, as demonstrated by smallangle X-ray scattering. The chain dimensions were found to be identical for the ionomer and ester, in agreement with the predictions of Squires et al. but in disagreement with the theories of Forsman and Dreyfus. Detailed analysis of the data showed that the contacts between the two isotopic types were random, as intended. The data were satisfactorily described by a polydisperse assembly of wormlike chains, with a Kuhn statistical length comparable to that for homopolystyrene. [less ▲]

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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 detailSolution behavior of α,ω-(dimethylamino)polyisoprene coordinated to transition metal salts
Charlier, Pascal; Jérôme, Robert ULg; Teyssié, Philippe

in Macromolecules (1990), 23(6), 1831-1837

Coordination of the amino end groups of a telechelic polymer to transition-metal salts has been found to modify profoundly the solution behavior of that material. In toluene, the relative viscosity ... [more ▼]

Coordination of the amino end groups of a telechelic polymer to transition-metal salts has been found to modify profoundly the solution behavior of that material. In toluene, the relative viscosity increases rapidly with concentration, in a way that depends on the transition metal. The coordination ability of the metal cations has been observed to be as follows: Ni < Co < Fe < Cu. The sharpness of the increase in viscosity upon increasing polymer concentration can be significantly reduced in a polar solvent and more effectively in a solvent able to compete with the amino end groups for the coordination sites of the transition metal. Moreover, the viscosity effect, and accordingly the association of the amino end groups, appears to be maximum at a Cu/amine molar ratio of 1. Any change in this ratio between 0.33 and 1.25 causes a drop in the solution viscosity. Empirical equations have been derived to fit the experimental hydrodynamic behavior. [less ▲]

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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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See detailSynthesis, characterization, and miscibility of caprolactone random copolymers
Vion, Jean-Marc; Jérôme, Robert ULg; Teyssié, Philippe et al

in Macromolecules (1986), 19(7), 1828-1838

The ring-opening polymerization and copolymerization of ε-caprolactone, ε-methyl-ε-caprolactone, β,δ-methyl-ε-caprolactone (mixed isomers), and L-lactide using aluminum isopropoxide as initiator were ... [more ▼]

The ring-opening polymerization and copolymerization of ε-caprolactone, ε-methyl-ε-caprolactone, β,δ-methyl-ε-caprolactone (mixed isomers), and L-lactide using aluminum isopropoxide as initiator were investigated. The chain propagation proceeds through a living anionic type coordinated insertion mechanism. The kinetic features of this process are reported. The experimental monomer reactivity ratios indicate that ε-caprolactone and its methyl derivatives yield random copolyesters. However, the ε-caprolactone/L-lactide pair exhibits a departure from randomness with the preferred incorporation of L-lactide units. The thermal properties of the copolymers were investigated by differential scanning calorimetry. It was found that the crystallization of ε-caprolactone units is limited, in all cases, to copolymers which are rich in this sort of unit. At the same time, the crystallization of L-lactide units was observed in copolymers with high concentrations of this comonomer. Analysis of the melting point depreasion data of the copolymers indicates that the L-lactide units are almost completely rejected from the caprolactone crystals, whereas about 50% of the ε-methyl-ε-caprolactone and δ,δ-methyl-ε-caprolactone comonomer units are incorporated into the ε-caprolactone crystals due to an obvious structural similarity. Finally, poly(ε-caprolactone-co-ε-methyl-ε-caprolactone) samples are miscible with poly(viny1 chloride) (PVC) whatever the composition of the copolymer and the composition of the blend, whereas poly(εt-caprolactone-co-L-lactide) samples are miscible with PVC uniquely for copolymer L-lactide contents equal to or smaller than 40 wt %. In all cases where miscibility was found, a negative thermodynamic interaction parameter was computed. [less ▲]

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See detailHalato-telechelic polymers. VI. Viscoelastic properties of solutions of alkaline earth α, ω-dicarboxylatopolybutadiene
Broze, Guy ULg; Jérôme, Robert ULg; Teyssié, Philippe et al

in Macromolecules (1983), 16(6), 996-1000

Alkaline earth alpha,omega-dicarboxylatopolybutadienesd issolved in a nonpolar solvent (an= 4600) display an attractive thermorheological simplicity and exhibit a secondary relaxation characteristic of ... [more ▼]

Alkaline earth alpha,omega-dicarboxylatopolybutadienesd issolved in a nonpolar solvent (an= 4600) display an attractive thermorheological simplicity and exhibit a secondary relaxation characteristic of the ionic component. The shear-thickening character of these solutions is to be outlined. Their deformation mechanism is controlled by the stability and the mean size of the ionic multiplets formed by the carboxylate end groups. The electrostatic origin of the viscoelastic behavior observed is well established by its dependence on solvent, temperature, and cation size. [less ▲]

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See detailHalato-telechelic polymers. IV - Synthesis and dilute-solution behavior
Broze, Guy ULg; Jérôme, Robert ULg; Teyssié, Philippe

in Macromolecules (1982), 15(3), 920-927

Halato-telechelic polymers (HTP) result from the complete ionization of both ends of telechelic prepolymers. Their behavior in nonpolar solvents is characterized by a very abrupt increase of viscosity at ... [more ▼]

Halato-telechelic polymers (HTP) result from the complete ionization of both ends of telechelic prepolymers. Their behavior in nonpolar solvents is characterized by a very abrupt increase of viscosity at increasing concentration, so that gel formation is noted at concentrations as low as 1.5 gdL-'. The nature of the ion pairs, polarity of the medium, and temperature influence significantly the gel formation and prove its electrostatic origin. The depressive effect of any polar additive on the gelation requires drastic conditions in the synthesis of reproducible materials. In this respect, an efficient synthetic pathway has been proposed. The influence of molecular weight and end-to-end distance of the prepolymer shows the determinant role played by the polymeric backbone on the ion aggregation process. [less ▲]

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See detailPolycaprolactone-based block copolymers. I - Synthesis by anionic-coordination type catalysts
Heuschen, J.; Jérôme, Robert ULg; Teyssié, Philippe

in Macromolecules (1981), 14(2), 242-246

Bimetallic µ-oxalok oxides are very active anionic coordination type catalysts in the living polymerization of t-caprolactone. These compounds have a well-defined composition which can be systematically ... [more ▼]

Bimetallic µ-oxalok oxides are very active anionic coordination type catalysts in the living polymerization of t-caprolactone. These compounds have a well-defined composition which can be systematically modified. It is proposed that at least half the alkoxy groups of these catalysts are replaced by carboxylate ones and the remaining alkoxy groups by any hydroxyl-terminated polymer PX. These new polymer PX-supported catalysts are powerful tools in tailoring poly(ε-capro1actone) block copolymers with well controlled molecular parameters. [less ▲]

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See detailSoluble bimetallic μ-oxo-alkoxides. 8. Structure and kinetic behavior of the catalytic species in unsubstituted lactone ring-opening polymerization
Ouhadi, T.; Hamitou, A.; Jérôme, Robert ULg et al

in Macromolecules (1976), 9(6), 927-931

The bimetallic µ-oxo-alkoxides are highly active for lactone ring-opening polymerization. These compounds are aggregated in solution and their mean degree of association depends on the nature of alkoxide ... [more ▼]

The bimetallic µ-oxo-alkoxides are highly active for lactone ring-opening polymerization. These compounds are aggregated in solution and their mean degree of association depends on the nature of alkoxide groups, metals, and solvent; it is modified by addition of suitable ligands or temperature variations. The course of the lactone polymerization is strongly related to the structural features of the catalyst. The determination of the mean number of growing chains per catalyst molecule, the study of the polymerization kinetics, and the knowledge of the catalyst behavior during the monomer conversion have contributed to an understanding of the polymerization mechanism. [less ▲]

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