References of "Dubois, Philippe"
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See detailDual Multimodular Class a Penicillin-Binding Proteins in Mycobacterium Leprae
Lepage, Sophie; Dubois, Philippe ULg; Ghosh, Thushar-Kanti et al

in Journal of Bacteriology (1997), 179(14), 4627-4630

The ponA gene of cosmid L222 of the Mycobacterium leprae genome library encodes a multimodular class A penicillin-binding protein (PBP), PBP1. The PBP, labelled with a polyhistidine sequence, has been ... [more ▼]

The ponA gene of cosmid L222 of the Mycobacterium leprae genome library encodes a multimodular class A penicillin-binding protein (PBP), PBP1. The PBP, labelled with a polyhistidine sequence, has been produced in Escherichia coli, extracted from the membranes with 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane-sulfonate (CHAPS) and purified by Ni2(+)-nitrilotriacetic acid-agarose chromatography. In contrast to the pon1-encoded class A PBP1, PBP1 undergoes denaturation at temperatures higher than 25 degrees C, it catalyzes acyl transfer reactions on properly structured thiolesters, and it binds penicillin with high affinity. [less ▲]

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See detailPolarised light induced birefringence in azo dye doped polymer: a new model and polarised holographic experiments
Blanche, Pierre-Alexandre ULg; Lemaire, P. C.; Maertens, Christophe et al

in Optics Communications (1997), 139(1-3), 92-98

The photoinduced birefringence of azo dye DMNPAA (2,5-dimelthyl-4-(p-nitrophenylazo)anisole) in PVK (Poly(N-vinylcarbazole)) thin film is reported. A two-layer model of the film is proposed to take into ... [more ▼]

The photoinduced birefringence of azo dye DMNPAA (2,5-dimelthyl-4-(p-nitrophenylazo)anisole) in PVK (Poly(N-vinylcarbazole)) thin film is reported. A two-layer model of the film is proposed to take into account the different results obtained in photoinduced birefringence experiments. According to this model, the sample exhibits intrinsic birefringence but the absorbed light can induce orientation of the optically active molecules contained in the first layer of the film, lending to photoinduced birefringence. Holographic experiments have been carried out in this media with recording at 514 nm and readout at 633 nm. Diffraction efficiency versus polarisation shows that these polymers can record polarisation states as well as intensity patterns. [less ▲]

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See detailSynthesis of novel conjugated oligomers for second-order nonlinear optics: incorporation of a central spacer as a conjugation modulator
Zhang, Jian Xang; Dubois, Philippe ULg; Jérôme, Robert ULg

in Journal of the Chemical Society. Perkin Transactions (1997), 2(6), 1209-1216

A new series of second-order nonlinear optical chromophores has been synthesized that consists of a conjugated segment end-capped with an electron acceptor and an electron donor, respectively, and a ... [more ▼]

A new series of second-order nonlinear optical chromophores has been synthesized that consists of a conjugated segment end-capped with an electron acceptor and an electron donor, respectively, and a central spacer intended to modulate the electro-optical effect. Conjugated chains have been tailored with trans-vinylene-1,5-thienylene as the building unit and N,N-dimethylamino and nitro groups as the donor–acceptor pair. Four spacers have been incorporated into the central part of the conjugated oligomers, which range from saturated to totally unsaturated functions, i.e. from methylene to vinylene units. The general strategy relies upon two consecutive Wittig or Wittig–Horner reactions between the spacer precursor and an aromatic phosphonium or phosphonate bearing the strong electron donor and the acceptor, respectively. Two synthetic pathways have been studied. The first procedure is based on the use of a symmetric precursor for the spacer. However, a reaction byproduct is formed, which must be removed and decreases the reaction efficiency. The second approach requires an asymmetric precursor for the spacer, the synthesis of which is a multistep process. In order to evaluate the effect of the spacer, a completely conjugated oligomer has been prepared by the one-step coupling of two conjugated segments end-functionalized by the electron donor and the acceptor, respectively. [less ▲]

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See detailBulk polymerization of lactides initiated by aluminium isopropoxide, 3a). Thermal stability and viscoelastic properties
Degée, Philippe; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecular Chemistry and Physics (1997), 198(6), 1985-1995

The thermal stability of poly(L-lactide) and L/D-lactide stereocopolymers polymerized in bulk with aluminium isopropoxide as initiator was investigated by thermogravimetric analysis, and time and ... [more ▼]

The thermal stability of poly(L-lactide) and L/D-lactide stereocopolymers polymerized in bulk with aluminium isopropoxide as initiator was investigated by thermogravimetric analysis, and time and température dependence of molecular weight and polydispersity. Compared to poly(L-lactide) prepared with stannous octoate as catalyst, the thermal stability of polylactides is remarkably enhanced when the ring-opening polymerization is initiated by aluminium alkoxide. Ultimate mechanical properties and viscoelasticity of these melt-stable thermoplastics have also been studied in relation to the polyester enan-tiomeric composition. [less ▲]

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See detailBulk polymerization of lactides initiated by aluminium isopropoxide, 2a). Beneficial effect of Lewis bases and transfer agents
Degée, Philippe; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecular Chemistry and Physics (1997), 198(6), 1973-1984

A high increase in the bulk polymerization rate of L,L-lactide and racemic D,L-lactide is observed when aluminium isopropoxide is added with an equimolar amount of a Lewis base, such as triphenylphosphine ... [more ▼]

A high increase in the bulk polymerization rate of L,L-lactide and racemic D,L-lactide is observed when aluminium isopropoxide is added with an equimolar amount of a Lewis base, such as triphenylphosphine (P(Φ)3) and better 4-picoline (C6H7N). Polylactide of high molecular weight and narrow molecular weight distribution is accordingly prepared in a controlled manner when the Al(OiPr)3 ; C6H7N combination is used as an initiator over a large temperature range from 110 to 180°C. A secondary alcohol, such as 2-propa-nol, has proved to be an efficient transfer agent, which allows the amount of Al per kg of polylactide to be advantageously reduced. All the alcohol molecules participate in the ring-opening polymerization even at an [iPrOH]0/[Al] ratio as high as 103. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 22. Copolymerization of ε-caprolactone and 1,4,8-trioxaspiro[4.6]-9-undecanone initiated by aluminum isopropoxide
Tian, Dong; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (1997), 30(9), 2575-2581

Novel biodegradable and biocompatible polyesters have been prepared by random copolymerization of ε-caprolactone (ε-CL) and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO) initiated by Al(OiPr)3. Copolyesters ... [more ▼]

Novel biodegradable and biocompatible polyesters have been prepared by random copolymerization of ε-caprolactone (ε-CL) and 1,4,8-trioxaspiro[4.6]-9-undecanone (TOSUO) initiated by Al(OiPr)3. Copolyesters of molecular weight (Mn) up to 104 and containing up to 90 mol % TOSUO repeating units have been prepared. The copolymer molecular weight is controlled by the molar ratio of the consumed comonomers and the initiator. The TOSUO constitutive units have been quantitatively deacetalized into ketones, which have also been efficiently reduced into hydroxyl groups without any apparent chain degradation. Therefore, poly(ε-caprolactone) (PCL) with well-defined content of ketone or hydroxyl pendent groups have been made available. The ε-CL and TOSUO comonomer units are randomly distributed within the copolymers, as assessed by the 13C-NMR sequence analysis. Indeed, the reactivity ratios (rC and rT) have been calculated from the average length of the ε-CL sequences (LC) and the TOSUO sequences (LT) and found to be 1.3 (rC) and 1.0 (rT), respectively. There is an interesting parallelism between the crystallinity and the average length of the ε-CL sequences. Copolyesters containing a molar fraction of TOSUO units smaller than 0.15 are semicrystalline, whereas the incorporation of larger amounts of TOSUO units results in amorphous copolyesters. Conversion of the ethylene acetal pendent groups into ketones and ultimately into hydroxyl pendent groups results in increasing glass transition temperature (Tg), melting temperature (Tm), and melting enthalpy (ΔHm). The thermal stability depends on the copolyester composition, since it decreases as the molar fraction of TOSUO units is increased. [less ▲]

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See detailMacromolecular engineering of polylactones and polylactides. 23. Synthesis and characterization of biodegradable and biocompatible homopolymers and block copolymers based on 1,4,8-trioxal [4.6] spiro-9-undecanone
Tian, Dong; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (1997), 30(7), 1947-1954

Homopolymers of 1,4,8-trioxa[4.6]spiro-9-undecanone (TOSUO) and block copolymers of TOSUO and ε-caprolactone (ε-CL) have been synthesized with aluminum isopropoxide as an initiator in toluene at 25 °C ... [more ▼]

Homopolymers of 1,4,8-trioxa[4.6]spiro-9-undecanone (TOSUO) and block copolymers of TOSUO and ε-caprolactone (ε-CL) have been synthesized with aluminum isopropoxide as an initiator in toluene at 25 °C. The homopolymerization is first order with respect to both monomer and initiator, and the end-group analysis agrees with a coordination−insertion mechanism based on the acyl-oxygen cleavage of the TOSUO ring. Living poly(ε-caprolactone) (PCL) and poly(1,4,8-trioxa[4.6]spiro-9-undecanone) (PTOSUO) chains are very efficient macroinitiators for the polymerization of TOSUO and ε-CL, respectively, with formation of block copolymers of a narrow molecular weight distribution. Size-exclusion chromatography (SEC) and 13C-NMR confirm the blocky structure of the copolymers, in agreement with DSC, which shows two glass transitions characteristic of the amorphous phase of PCL and PTOSUO, respectively. The ethylene ketal pendent groups of the PTOSUO block have been successfully converted to ketones and hydroxyl pendent groups without scission of the polyester backbone. These new materials have potential for applications in medicine, surgery, and tissue engineering. [less ▲]

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See detailStereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA: 1. Thermal and mechanical properties of stereocomplexes
Yu, Jian Ming; Yu, Yi-Song; Dubois, Philippe ULg et al

in Polymer (1997), 38(9), 2143-2154

A novel thermoplastic elastomer consisting of a triblock copolymer (MBM) with outer syndiotactic poly(methyl methacrylate) (sPMMA) blocks associated to an inner polybutadiene (PBD) block has been modified ... [more ▼]

A novel thermoplastic elastomer consisting of a triblock copolymer (MBM) with outer syndiotactic poly(methyl methacrylate) (sPMMA) blocks associated to an inner polybutadiene (PBD) block has been modified by stereocomplexation with isotactic PMMA (iPMMA). Solution cast films of stereocomplexes have been analysed by thermal analysis as a function of the iPMMA/sPMMA (i/s) mixing ratio and the solvent used for the film casting. Although self-aggregation of iPMMA is currently observed, this phenomenon does not occur in solvent cast films of iPMMA with the MBM copolymers. Extent of complexation depends on the i/s mixing ratio and the casting solvent. At a constant i/s ratio, molecular weight of iPMMA has no significant effect on the extent of stereocomplexation. Thermal stability of the stereocomplexes is only affected by the casting solvent, in contrast to tensile strength which is greatly influenced by the mixing ratio of the two PMMA stereoisomers. Tensile strength is increased when increasing amounts of iPMMA are blended with a triblock copolymer of low PMMA content (e.g. 12%). In case of triblocks of high PMMA content (ca. 30% or higher), a low i/s ratio (<l/4) increases the tensile strength, whereas a high i/s mixing ratio (1/2) results in decreasing tensile strength. The same trend is observed for blends of sPMMA-polystyrene (PS)-PBD-PS-sPMMA (MSBSM) pentablock copolymers with iPMMA. [less ▲]

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See detailA novel biodegradable and biocompatible ceramer prepared by the sol-gel process
Tian, Dong; Dubois, Philippe ULg; Grandfils, Christian ULg et al

in Chemistry of Materials (1997), 9(4), 871-874

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See detailRing-Opening Polymerization of 1,4,8-Trioxaspiro[4.6]-9-undecanone: A new Route to Aliphatic Polyesters Bearing Functional Pendent Groups
Tian, Dong; Dubois, Philippe ULg; Grandfils, Christian ULg et al

in Macromolecules (1997), 30(3), 406-409

A straightforward and very efficient pathway has been reported for the synthesis of a functional derivative of ε-caprolactone, i.e. 5-ethylene ketal ε-caprolactone. This new monomer has been ... [more ▼]

A straightforward and very efficient pathway has been reported for the synthesis of a functional derivative of ε-caprolactone, i.e. 5-ethylene ketal ε-caprolactone. This new monomer has been homopolymerized and copolymerized with ε-caprolactone in a well-controlled manner, strongly suggesting absence of any side reactions. Deacetalization of the polyester chains is complete and reduction of the ketone groups into hydroxyl groups as well. No chain scission is observed to occur in the course of these two derivatization reactions. Thus, aliphatic polyesters bearing either ketone pendent groups or hydroxyl pendent groups can be easily prepared, which raises new application prospects. These materials proved to be easily redispersed in an aqueous medium. They form stable colloidal nanodispersions (e.g. 100 nm). These suspensions are stable more than 48 h at room temperature and may be viewed as potential drug colloidal vectors with a core−shell like structure. Different types of reactive groups on the surface of these nanoparticulate vectors are indeed available to the binding of species selected for molecular recognition and drug targeting. For instance, the well-known reactivity of ketones toward primary amines is a direct route to attach peptides onto biodegradable and biocompatible aliphatic polyesters. Poly(ε-caprolactone) with hydroxyl groups reactive toward triethylaluminum provides a macroinitiator for lactone and lactide polymerization, so that biodegradable and biocompatible functional comb, graft, and dendritic aliphatic polyesters can now be synthesized. [less ▲]

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See detailSynthesis and characterization of biodegradable homopolymers and block copolymers based on adipic anhydride
Ropson, Nathalie; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1997), 35(1), 183-192

Homopolymers of adipic anhydride (AA) and block copolymers of -caprolactone (-CL) and AA have been synthesized with aluminum triisopropoxide as an initiator. Homopolymerization was studied at 20°C in ... [more ▼]

Homopolymers of adipic anhydride (AA) and block copolymers of -caprolactone (-CL) and AA have been synthesized with aluminum triisopropoxide as an initiator. Homopolymerization was studied at 20°C in toluene and methylene chloride (CH2Cl2). The end-group analysis agrees with a coordination insertion mechanism based on the acyl-oxygen cleavage of the AA ring. Living poly(-caprolactone) (PCL) chains are very efficient macro-initiators for the polymerization of AA, with formation of diblock copolymers of a narrow molecular weight distribution. At our best knowledge, low molecular weight -aluminum alkoxide PCL macroinitiators (M¯n < 1000) allow the first valuable synthesis of PAA with a molecular weight as high as 58,000 and a quite narrow polydispersity (M¯w/M¯n = 1.2). Size-exclusion chromatography (SEC) and 13C NMR confirm the blocky structure of the copolymers, in agreement with DSC that shows two melting endotherms and two glass transitions characteristic of the crystalline and amorphous phases of PCL and PAA, respectively. Block copolymers of c-CL and AA are also sensitive to hydrolysis, which makes them possible candidates for biomedical applications. Initiation of the AA polymerization in bulk with aluminum triisopropoxide in the presence of various ligands is also discussed. [less ▲]

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See detailLiving free radical polymerization of macromonomers: preparation of well defined graft copolymers
Hawker, Craig Jon; Mecerreyes, David; Elce, Edmund et al

in Macromolecular Chemistry and Physics (1997), 198(1), 155-166

Well defined graft copolymers have been synthesized by a nitroxide-mediated "living" free radical process using pre-formed macromonomers. Analysis of the graft systems revealed that the macromonomer was ... [more ▼]

Well defined graft copolymers have been synthesized by a nitroxide-mediated "living" free radical process using pre-formed macromonomers. Analysis of the graft systems revealed that the macromonomer was efficiently incorporated into the polymeric back-bone to give block copolymers of controlled molecular weight and narrow polydispersi-ties. An added benefit of the "living" free radical process is that macromonomers, such as polylactide or polycaprolactone, which contain reactive functional groups can be used to form novel graft Systems using this approach. Functionalized monomers or polymeric initiators were also used in the copolymerization mixture to give graft Systems with a variety of functional groups attached to the backbone. [less ▲]

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See detailCarbon black-filled polymer blends : a scanning probe microscopy characterization
Leclère, Philippe; Lazzaroni, Roberto; Gubbels, Frédéric et al

in Materials Research Society Symposium Proceedings (1997), 457

Conducting polymer composites, that consist of a conducting filler randomly distributed throughout an insulating polymer or polymer blend, attract interest in several application fields such as sensors or ... [more ▼]

Conducting polymer composites, that consist of a conducting filler randomly distributed throughout an insulating polymer or polymer blend, attract interest in several application fields such as sensors or electromagnetic radiation shielding. The macroscopic electrical resistivity of the filled polyblend strongly depends on the localization of the filler. Here, we investigate the morphology of Carbon Black (CB)-filled polymer blends in order to determine the parameters governing the selective localization of CB in one phase of the blend components or at the interface between the components. The dispersion of the CB particles in the polymer blend is observed by means of Lateral Force Microscopy (LFM) as a function of the blend composition and the load in CB. The selective localization of CB at the interface enables the reduction of the percolation threshold down to 0.5 wt%; as a result, the mechanical properties of the polymer blend can be fully retained. Different techniques can be used to locate the CB at the interface; we compare their efficiency experimentally. [less ▲]

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See detailSynthesis and properties of poly[isobornyl methacrylate (IBMA)-b-butadiene (BD)-b-IBMA] copolymers : new thermoplastic elastomers of a large service temperature range
Yu, Jian Ming; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (1996), 29(16), 7316-7332

Anionic polymerization of isobornyl methacrylate (IBMA) has been studied in THF and toluene in a temperature range from −78 to +40 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as an ... [more ▼]

Anionic polymerization of isobornyl methacrylate (IBMA) has been studied in THF and toluene in a temperature range from −78 to +40 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as an initiator in the presence of LiCl or not. Effect of solvent and polymerization temperature on tacticity has been studied. The reactivity of IBMA is comparable to tert-butyl methacrylate (tBMA), and polymers of a very narrow molecular weight distribution (<1.10) have been synthesized at room temperature, in THF, in the presence of LiCl. The Tg of PIBMA is found to vary from 170 to 206 °C with chain tacticity. Poly(isobornyl methacrylate) (PIBMA)−polybutadiene (PBD)−PIBMA triblock copolymers have been synthesized by using the m-diisopropenylbenzene (m-DIB)/tert-butyllithium (t-BuLi) diadduct as an initiator. The PBD midblock has been prepared in a cyclohexane/diethyl ether (100/6, v/v) mixture at room temperature. THF has been added [cyclohexane/diethyl ether/THF (100/6/100, v/v/v)] before the IBMA polymerization takes place at either −78 or +25 °C. Triblock copolymers of a very narrow molecular weight distribution (1.10) have been synthesized even at 25 °C, and no gel formation has been observed. These new triblock copolymers exhibit high tensile strength (30 MPa), high ultimate elongation (1000%), and high upper service temperature (160 °C). [less ▲]

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See detailSAXS analysis of the morphology of biocompatible and biodegradable poly(ε-caprolactone-b-glycolide) copolymers1
Sobry, R.; Van den Bossche, Guy ULg; Fontaine, F. et al

in Journal of Molecular Structure (1996), 383(1-3), 63-68

Poly(epsilon-caprolacrone-b-glycolide) diblock copolyesters have been synthesized by the sequential polymerization of epsilon-caprolactone and glycolide as initiated by aluminium alkoxides ... [more ▼]

Poly(epsilon-caprolacrone-b-glycolide) diblock copolyesters have been synthesized by the sequential polymerization of epsilon-caprolactone and glycolide as initiated by aluminium alkoxides. Copolymerization is typically ''living'' and yields copolyesters of perfectly controlled molecular weight and composition. Diblock molecular weight (Mn-PGA+Mn-PCL) ranges from 5700 to 42000 and the rho = Mn-PCL/Mn-PGA ratio varies from 1.5 to 13.1. Due to the inherent insolubility of the polyglycolide (PGA) segment in common organic solvent, the diblock copolyesters form stable non-aqueous colloidal dispersions e.g. in toluene, the stability of which results from the soluble poly(epsilon-caprolactone) (PCL) block. Combining all the experimental observations (PCS, TEM, WAXS, SAXS, AFM), a micelle model has been proposed which consists of a polyglycolide core surrounded with a corona of polycaprolactone (PCL). Both constituents are semi crystalline. From SAXS observations, the PGA core is better described by two concentric spheres. The internal sphere of a 5-6.7 nn diameter would essentially contain crystalline PGA. The diameter of the external sphere, D-PGA, is in the range from 6.2 to 9.6 nm, at least for the investigated diblock copolymers. As a rule, this diameter increases as rho decreases at constant molecular weight and as the diblock molecular weight increases at constant rho. A scattering peak (weak) is observed in the range from 10.8 to 15.5 nm and the Bragg distance is close mu D-PGA, where mu is equal to (1+3 rho/2)(1/3). From steric considerations, mu is the ratio between the diameter of the micelle and the diameter of the PGA core, so that this peak has been assigned to the characteristic intermicellar distance. At very small angles, several additional peaks are the signature of a hyperstructure which is possibly lamellar. [less ▲]

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See detailMicrodomain morphology analysis of block copolymers by atomic force microscopy with phase detection imaging
Leclère, Philippe; Lazzaroni, Roberto; Brédas, Jean-Luc et al

in Langmuir (1996), 12(18), 4317-4320

We use atomic force microscopy (AFM) with phase detection imaging (PDI) in order to study the surface microdomain morphology of thick (i.e., ca. 2 mm) films of triblock copolymers. We present here the ... [more ▼]

We use atomic force microscopy (AFM) with phase detection imaging (PDI) in order to study the surface microdomain morphology of thick (i.e., ca. 2 mm) films of triblock copolymers. We present here the results obtained on a poly(methyl methacrylate)-block-polybutadiene-block-poly(methyl methacrylate) (PMMA-b-PBD-b-PMMA) copolymer prepared by using a 1,3-diisopropenylbenzene (DIB)-based difunctional anionic initiator. Our data illustrate the interest of PDI for the elucidation of surface phase separation in block copolymers. We show that the surface of thick films studied by this new technique exhibits a two-phase structure corresponding to the two types of components. [less ▲]

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See detailSyndiotactic poly(methyl methacrylate) (sPMMA)-polybutadiene (PBD)-sPMMA triblock copolymers: synthesis, morphology, and mechanical properties
Yu, Jian Ming; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Macromolecules (1996), 29(19), 6090-6099

A series of syndiotactic poly(methyl methacrylate) (sPMMA)−polybutadiene (PBD)−sPMMA triblock copolymers, or MBM, have been successfully synthesized by using dilithium initiators (DLi's) based on the ... [more ▼]

A series of syndiotactic poly(methyl methacrylate) (sPMMA)−polybutadiene (PBD)−sPMMA triblock copolymers, or MBM, have been successfully synthesized by using dilithium initiators (DLi's) based on the diadduct of tert-butyllithium (t-BuLi) to either 1,3-bis(1-phenylethenyl)benzene (PEB) or m-diisopropenylbenzene (m-DIB). The efficiency of these DLi's in building up MBM triblock copolymers has been compared under the same experimental conditions, i.e., in a cyclohexane/diethyl ether mixture for the butadiene polymerization at room temperature and in a cyclohexane/THF mixture for the MMA polymerization at −78 °C. Although all the synthesized copolymers show a monomodal, symmetric, and very narrow molecular weight distribution, the MBM copolymers synthesized with the m-DIB/t-BuLi diadduct are pure triblocks and show a high tensile strength, in contrast to copolymers initiated by the PEB/t-BuLi diadducts that are of a lower tensile strength and contaminated by MB diblock copolymers. Solvent cast films of MBM prepared with the m-DIB/t-BuLi diadduct are two-phase materials as confirmed by DSC and dynamic mechanical analysis (DMA). Transmission electron microscopy (TEM) shows a spherical morphology at a low sPMMA content, that changes into a cylindrical and finally lamellar morphology upon increasing the sPMMA content. Phase separation is observed for MBM with M̄n of the sPMMA blocks as low as 6000. Dependence of tensile strength on copolymer structure and sample preparation has been studied. The smaller sPMMA molecular weight, M̄n(PMMA), required for high tensile strength depends on the PBD molecular weight, M̄n(PBD), e.g. 12 000 for Mn(PBD) = 36 000 and 6000 for Mn(PBD) = 80 000. The upper M̄n(PMMA) is ca. 20−25 000, whatever the Mn(PBD). The optimum tensile strength is observed for M̄n(PMMA) = 15 000, independently of Mn(PBD) in the studied range. As a rule, the tensile strength tends to level off and the elongation at break starts to decrease when the sPMMA content is increased beyond 35 wt %. At a constant sPMMA content, Mn(PBD) (>ca. 36 000) does not affect the ultimate tensile properties. [less ▲]

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See detailDifunctional initiator based on 1,3-diisopropenylbenzene. 4. Synthesis and modification of poly(alkyl methacrylate-b-styrene-b-butadiene-b-styrene-b-alkyl methacrylate (MSBSM) thermoplastic elastomers
Yu, Y. S.; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Journal of Polymer Science. Part A, Polymer Chemistry (1996), 34(11), 2221-2228

MSBSM five-block copolymers where B stands for butadiene, S for styrene, and M for either methyl methacrylate (MMA) or tert-butyl methacrylate (tBMA) have been synthesized by sequential anionic ... [more ▼]

MSBSM five-block copolymers where B stands for butadiene, S for styrene, and M for either methyl methacrylate (MMA) or tert-butyl methacrylate (tBMA) have been synthesized by sequential anionic polymerization in an apolar solvent by using a difunctional anionic initiator derived from 1,3-diisopropenylbenzene. These block copolymers show improved mechanical properties and an extended service temperature compared to traditional SBS thermoplastic elastomers. Upon hydrolysis and further neutralization of the PolytBMA end-blocks, the upper glass transition temperature (Tg) of the five-block copolymers has been raised up to about 150°C. A further increase in this service temperature (up to ca. 160°C) has resulted from the blending of sPMMA-SBS-sPMMA five-block copolymers with isotactic poly(methacrylate) (iPMMA), due to the formation of a stereocomplex. The tensile properties of these modified five-block copolymers have remained essentially unchanged. [less ▲]

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See detailA new poly (ε-caprolactone) containing hybrid ceramer prepared by the sol-gel process
Tian, Dong; Dubois, Philippe ULg; Jérôme, Robert ULg

in Polymer (1996), 37(17), 3983-3987

A new inorganic-organic hybrid material, known as ceramer, has been prepared by the sol-gel process. α,ω-Hydroxyl poly(ε-caprolactone) (PCL) has been used as an organic reagent, as such or after ... [more ▼]

A new inorganic-organic hybrid material, known as ceramer, has been prepared by the sol-gel process. α,ω-Hydroxyl poly(ε-caprolactone) (PCL) has been used as an organic reagent, as such or after conversion of the hydroxyl end-groups into triethoxysilane end-groups. The novelty has to be found in the biocompatibility and biodegradability of the organic constitutive component. Since the hydroxyl end-groups of PCL are less reactive than the triethoxysilane counterparts, the preliminary reaction of the hydroxyl end-groups with 3-isocyanatopropyltriethoxysilane is recommended for decreasing the gelation time and the amount of PCL extractable from the final hybrid material. In this respect, it has been observed that the amount of PCL incorporated into the network is limited by the early vitrification of the reactive system. This drawback can be alleviated by curing the sample at a high enough temperature (100°C). TEM observations have shown that the organic and inorganic phases are intimately mixed when the weight composition in SiO2 and PCL is close to 50%. [less ▲]

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