References of "Polymer"
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See detailDetermination of the stability constants of uranyl/polymer complexes by differential pulse polarography
Leroy, D.; Martinot, Lucien; Jérôme, Christine ULg et al

in Polymer (2001), 42(10), 4589-4596

Differential pulse polarography (DPP) allows for the determination of the stability constants (K) and the stoichiometry (n) for the complexation of the UO22+ ion by various monomers and the parent ... [more ▼]

Differential pulse polarography (DPP) allows for the determination of the stability constants (K) and the stoichiometry (n) for the complexation of the UO22+ ion by various monomers and the parent polymers. The experimental observation is the shift of the totally reversible reduction wave UO22++e- UO2+ toward more cathodic potentials when the complexing monomer or polymer is added to an uranyl nitrate aqueous solution. This shift is, however, much greater when the polymer is used rather than the monomer, in line with a higher stability of the complexes (Kpolymer>>Kmonomer). A theoretical stability scale of the polymers/UO22+ complexes was compared to an experimental one based on dynamic leaching tests. [less ▲]

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See detailTernary polymer blend with core-shell dispersed phases: effect of the core-forming polymer on phase morphology and mechanical properties
Luzinov, Igor; Pagnoulle, Christophe; Jérôme, Robert ULg

in Polymer (2000), 41(19), 7099-7109

Phase morphology and mechanical properties of ternary blends consisting of PS (polystyrene), SBR (styrene butadiene rubber) and different polyolefins (POs) have been studied. PS, systematically forms the ... [more ▼]

Phase morphology and mechanical properties of ternary blends consisting of PS (polystyrene), SBR (styrene butadiene rubber) and different polyolefins (POs) have been studied. PS, systematically forms the matrix, SBR and PO being combined in the dispersed phase. Although POs of various melt viscosity and stiffness are used, the binary (SBR/PO) dispersed phase is of a core-shell structure, in which PO forms the core. Upon increasing the viscosity of PO, the average size of the cores and the SBR domains including them increases. Comparison of the experimental shear storage modulus of the blends with theoretical predictions indicates that the stress transfer from the PS matrix to the PO core through the SBR shell depends on the modulus of the SBR envelope. The ultimate mechanical properties of the ternary blends are sensitive to the stiffness of the PO core. [less ▲]

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See detailReactive compatibilization of PC/PVDF polymer blends by zinc carboxylate containing poly(methylmethacrylate)ionomers
Moussaif, Noureddine; Pagnoulle, Christophe; Jérôme, Robert ULg

in Polymer (2000), 41(15), 5551-5562

Polycarbonate (PC) has been reacted with a random copolymer of methylmethacrylate and 6 mol% of acrylic acid (poly(MMA-co-AA)) and with this copolymer neutralized (totally or not) by Zn cations. When ... [more ▼]

Polycarbonate (PC) has been reacted with a random copolymer of methylmethacrylate and 6 mol% of acrylic acid (poly(MMA-co-AA)) and with this copolymer neutralized (totally or not) by Zn cations. When conducted in solution at 240°C, the reaction leads to the grafting of PC onto the copolymer neutralized or not. In the melt at 235°C, the grafting reaction occurs only when the copolymer is at least partly neutralized. Whatever the experimental conditions (solution or bulk), PMMA does not react with PC, which confirms that the acidolysis of PC is at the origin of the grafting reaction. Poly(vinylidene fluoride) (PVDF) and PC have been melt blended at 235°C in the presence of the poly(MMA-co-AA) copolymer totally neutralized or not by Zn cations, the purpose being the reactive formation of PMMA-g-PC copolymer that would act as compatibilizer for the PC/PVDF blend. The phase morphology and the mechanical properties of the compatibilized PC/PVDF blends have been compared with the parent non-reactive polyblends. Compared to the modification of PVDF by 20 wt% of PMMA, the use of 20 wt% of the partly neutralized poly(MMA-co-AA) copolymer decreases further the average size of the dispersed phase, enhances its adhesion to the matrix, and results in a considerable increase of the elongation at break. The beneficial effect of zinc carboxylate in the PMMA copolymer is explained by the grafting of PC onto PMMA at the interface. [less ▲]

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See detailAnionic synthesis of cyclic anhydride end-capped poly(methyl methacrylate)
Fallais, Isabelle; Pantoustier, Nadège; Devaux, Jacques et al

in Polymer (2000), 41(14), 5535-5539

This paper reports on the anionic synthesis of poly(methyl methacrylate) chains end-capped by cyclic anhydride. The method is based on the chemical derivatization of a precursor tert-butyl diester end ... [more ▼]

This paper reports on the anionic synthesis of poly(methyl methacrylate) chains end-capped by cyclic anhydride. The method is based on the chemical derivatization of a precursor tert-butyl diester end-group. Compared to the thermal modification, which was previously used, this method allows intermolecular coupling and polymer degradation to be avoided. But up to now, the final anhydride content remains moderate and has still to be improved. [less ▲]

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See detailSynthesis and bulk properties of poly(methyl methacrylate)-b-poly(isooctyl acrylate(isooctyl acrylate)-b-poly(methyl methacrylate)
Tong, J. D.; Leclère, Philippe; Doneux, C. et al

in Polymer (2000), 41(12), 4617-4624

A series of well-defined poly(methylmethacrylate) (PMMA)-b-poly(isooctylacrylate) (PIOA)-b-PMMA triblock copolymers (MIM) has been synthesized by transalcoholysis of PMMA-b-poly(tert-butylacrylate) (PtBA ... [more ▼]

A series of well-defined poly(methylmethacrylate) (PMMA)-b-poly(isooctylacrylate) (PIOA)-b-PMMA triblock copolymers (MIM) has been synthesized by transalcoholysis of PMMA-b-poly(tert-butylacrylate) (PtBA)-b-PMMA precursors (MTM) by isooctyl alcohol. Phase separation is observed for all the investigated triblock copolymers, thus containing PMMA outer blocks in the 3500-50,000 molecular weight (MW) range and PIOA inner block with MW in the 100,000-300,000 range. The ultimate tensile properties of these MIM triblock copolymers are poor even when PMMA blocks of 50,000 MW are associated with an inner PIOA block of 300,000 MW. A reasonable explanation should be found in the molecular weight between chain entanglements (Me), which has been estimated at 60,000 for PIOA, much higher than Me for the traditional polydiene central blocks in the well-known thermoplastic elastomers of the triblock type. The tensile behavior of MIM copolymers has been successfully accounted for by a simple elastomer model free from chain entanglements, supporting the view that the lack of entanglements in the central block is very detrimental to the mechanical properties of the investigated fully (meth)acrylate triblock copolymers. [less ▲]

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See detailDependence of phase morphology and mechanical properties of PS/SBR/PE ternary blends on composition: transition from core-shell to triple-phase continuity structures
Luzinov, Igor; Pagnoulle, Christophe; Jérôme, Robert ULg

in Polymer (2000), 41(9), 3381-3389

The weight ratio of PE and PS in ternary PS/SBR/PE blends has been changed at constant SBR content (25 wt%). When the matrix is either PE or PS, the dispersed phase has a core-shell structure with SBR ... [more ▼]

The weight ratio of PE and PS in ternary PS/SBR/PE blends has been changed at constant SBR content (25 wt%). When the matrix is either PE or PS, the dispersed phase has a core-shell structure with SBR forming the shell. The size of the core expectedly increases with the content of the core-forming polymer. In some composition range, the three phases are simultaneously continuous, SBR being localized in between the co-continuous PE and PS phases. The ultimate mechanical properties of the ternary blends containing SBR/PE and SBR/PS core-shell dispersed phases are close to the properties of the PS/SBR and PE/SBR binary blends, respectively. Some synergism in the elongation at break of the ternary blends is observed when core-shell SBR/PS phases are dispersed in PE matrix. [less ▲]

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See detailSingle-step reactive extrusion of PLLA in a corotating twin-screw extruder promoted by 2-ethylhexanoic acid tin(II) salt and triphenylphosphine
Jacobsen, S.; Fritz, H. G.; Degée, Philippe et al

in Polymer (2000), 41(9), 3395-3403

The ring opening polymerisation of L,L-lactide using an equimolar complex of 2-ethylhexanoic acid tin(II) salt Sn(Oct)2 and triphenylphosphine P( )3 as catalyst shows for the first time a reactivity ... [more ▼]

The ring opening polymerisation of L,L-lactide using an equimolar complex of 2-ethylhexanoic acid tin(II) salt Sn(Oct)2 and triphenylphosphine P( )3 as catalyst shows for the first time a reactivity providing a polymerisation propagation rate fast enough to imagine a continuous single-step reactive extrusion process for bulk polymerisation. The ring opening polymerisation has been realised on a corotating closely intermeshing twin-screw extruder, using a specially designed screw concept to provide sufficient energy input and mixing for further enhancement of the propagation rate, without detrimentally enhancing depolymerisation or transesterification reactions. Using one chosen screw and processing concept on a twin-screw extruder with 25 mm diameter and a L/D-ratio of 48, the influence of different processing parameters on the resulting molecular parameters of the Polylactide (PLA) has been determined. Furthermore, the mechanical property profile of the generated PLA-polymers is discussed and related to the molecular parameters. [less ▲]

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See detailXPS analysis of the PC/PVDF interface modified by PMMA. Location of the PMMA at the interface
Moussaif, Noureddine; Pagnoulle, Christophe; Riga, Joseph et al

in Polymer (2000), 41(9), 3391-3394

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be ... [more ▼]

Polycarbonate (PC) and polyvinylidenefluoride (PVDF) are two immiscible polymers, which form two-phase polyblends with a weak interfacial adhesion and a high interfacial tension. This situation may be changed by the addition of polymethylmethacrylate (PMMA), which is miscible with PVDF and concentrates at the PVDF/PC interface. Location of PMMA at the PC/PVDF interface has been confirmed by XPS analysis, which shows that the interface enrichment in PMMA already takes place when only 10 wt% PMMA is premixed with PVDF. [less ▲]

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See detailSynthesis of poly(methyl methacrylate)-b-poly(n-butyl acrylate)-b-poly(methyl methacrylate) triblocks and their potential as thermoplastic elastomers
Tong, J. D.; Jérôme, Robert ULg

in Polymer (2000), 41(7), 2499-2510

A series of well defined poly(methyl methacrylate) (PMMA)-b-poly(n-butyl acrylate) (PnBA)-b-PMMA triblock copolymers (MnBM) has been synthesized by transalcoholysis of PMMA-b-poly(tert-butylacrylate ... [more ▼]

A series of well defined poly(methyl methacrylate) (PMMA)-b-poly(n-butyl acrylate) (PnBA)-b-PMMA triblock copolymers (MnBM) has been synthesized by transalcoholysis of PMMA-b-poly(tert-butylacrylate) (PtBA)-b-PMMA precursors (MTM) by n-butanol. Phase separation is observed for all the investigated triblock copolymers, which contain PMMA outer blocks in the 5000-50 000 molecular weight (MW) range and PnBA inner blocks with MW in the 100 000-200 000 range. Although the ultimate tensile properties of these MnBM triblock copolymers are poor compared to traditional diene-based TPEs (SBS and SIS), they are much better than those ones reported for PMMA-b-poly(isooctyl acrylate) (PIOA)-b-PMMA triblocks (MIM). A reasonable explanation for this observation is found in the average molecular weight between chain entanglements (Me) that has been estimated to be 28 000 for the central PnBA rubbery block, which is consistently much smaller than for PIOA (59 000) and substantially higher than Me for polybutadiene (1700) and polyisoprene (6100). The tensile behavior of MnBM copolymers cannot be fitted by either a simple elastomer model free from chain entanglements (suitable to MIM) or by a "filler" modified rubber model (suitable for diene-based TPEs), supporting the hypothesis that the mechanical properties of the investigated (meth)acrylate thermoplastic elastomers are significantly affected by any change in Me of the central acrylate block. Viscoelastic analysis shows that MnBM triblocks are of higher complex viscosity than the SBS and SIS analogs, leading to a shift in the order-disorder transition temperature to much higher temperature, unless the outer PMMA blocks are of very low molecular weight (5000). [less ▲]

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See detailMiscibility of poly(vinylidene fluoride) and poly(methylmethacrylate-co-zinc polyacrylate) ionomers
Moussaif, Noureddin; Jérôme, Robert ULg

in Polymer (1999), 40(24), 6831-6839

A random copolymer of methyl methacrylate and 5.7 mol.% of acrylic acid has been neutralized by zinc cation to different extents in order to study the effect of zinc carboxylate pendant groups on the ... [more ▼]

A random copolymer of methyl methacrylate and 5.7 mol.% of acrylic acid has been neutralized by zinc cation to different extents in order to study the effect of zinc carboxylate pendant groups on the miscibility of poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF). The interaction parameter (χ) has been calculated from the experimental depression of the PVDF melting point. χ is minimum at zinc carboxylate content of 2.8 mol.%. The dynamic mechanical analysis of the PVDF-PMMA ionomer binary blends does not agree with the additivity rule of the properties, consistently with the phase morphology that changes with composition. Blends are indeed amorphous as long as the PVDF content does not exceed 40 wt.%, otherwise, semicrystalline PVDF coexists with an amorphous mixed PVDF/copolymer phase. [less ▲]

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See detailCompatibilization of immiscible polymer blends (PV/PVDF) by the addition of a third polymer (PMMA): analysis of phase morphology and mechanical properties
Moussaif, Noureddin; Jérôme, Robert ULg

in Polymer (1999), 40(14), 3919-3932

Compatibilization of the immiscible polycarbonate (PC)/polyvinylidenefluoride (PVDF) pair by a third homopolymer, i.e. polymethylmethacrylate (PMMA), was studied in relation to phase morphology and ... [more ▼]

Compatibilization of the immiscible polycarbonate (PC)/polyvinylidenefluoride (PVDF) pair by a third homopolymer, i.e. polymethylmethacrylate (PMMA), was studied in relation to phase morphology and mechanical properties of the polyblends. Scanning electron microscopy showed a more regular and finer phase dispersion when the original PMMA content in PVDF exceeded 20 wt.%. The premixing of PVDF with ca. 40 wt.% PMMA also had a beneficial effect on mechanical properties, such as ultimate tensile strength, elongation at break, and notched impact strength. All these experimental results are consistent with the interfacial activity of PMMA in the PC/PVDF blends. [less ▲]

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See detailComposition effect on the core-shell morphology and mechanical properties of ternary polystyrene/styrene-butadiene rubber/polyethylene blends
Luzinov, Igor; Xi, K.; Pagnoulle, Christophe et al

in Polymer (1999), 40(10), 2511-2520

The morphology of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends has been investigated in the limits of a constant content of the major component (PS; 75 wt%) while changing ... [more ▼]

The morphology of ternary polystyrene/styrene-butadiene rubber/polyethylene (PS/SBR/PE) blends has been investigated in the limits of a constant content of the major component (PS; 75 wt%) while changing the weight ratio of the two minor constitutive polymers. A core-shell structure for the dispersed phase has been predicted from the spreading coefficients and observed by transmission electron microscopy. Actually, upon increasing the relative content of PE with respect to SBR, the structure of the dispersed phase changes from a multicore structure to a PE/SBR core-shell morphology. The size of the PE subphase in the mixed dispersed phase increases sharply at a PE content that corresponds to phase inversion in the parent SBR/PE binary blends. The ultimate mechanical properties of these blends are sensitive to the strength of the SBR interphase between PS and PE. Some synergism has been observed in the PE/SBR composition dependence of the tensile strengths at yield and break. [less ▲]

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See detailBiodegradable and biocompatible inorganic-organic hybrid materials: 4. Effect of acid content and water content on the incorporation of aliphatic polyesters into silica by the sol-gel process
Tian, Dong; Blacher, Silvia ULg; Jérôme, Robert ULg

in Polymer (1999), 40(4), 951-957

The extent of poly -caprolactone (PCL) incorporation into silica networks prepared by the sol-gel process depends on the HCl:tetraethoxysilane (TEOS) molar ratio and the H2O:TEOS molar ratio, as well. The ... [more ▼]

The extent of poly -caprolactone (PCL) incorporation into silica networks prepared by the sol-gel process depends on the HCl:tetraethoxysilane (TEOS) molar ratio and the H2O:TEOS molar ratio, as well. The PCL incorporation increases with the concentration of the acid used as the catalyst. Dynamic mechanical analysis (DMA) indicates that increasing the acid concentration or decreasing the water content results in a higher glass transition temperature for the organic component in the hybrid materials, whereas the modulus does not change significantly. Small-angle X-ray scattering (SAXS) data agree with a nanoscopic phase separation of the two constitutive components: the organic polymer and the silica network. The characteristic length of this two-phase structure increases with acid content (except for the lower HCl:TEOS molar ratio of 0.05) and with water content (except for the higher H2O:TEOS molar ratio of 2.0). The structure of the PCL/SiO2 interface is mass fractal and the structure is more open when the acid content is lower or the water content higher. [less ▲]

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See detailStereocomplexation of sPMMA-PBD-sPMMA triblock copolymers with isotactic PMMA. II: Effect of molecular weight
Yu, Jian Ming; Jérôme, Robert ULg

in Polymer (1998), 39(25), 6567-6575

Thermoplastic elastomers consisting of triblock copolymers (MBM) with outer syndiotactic poly(methyl methacrylate) (sPMMA) blocks associated to an inner polybutadiene (PBD) block have been modified by ... [more ▼]

Thermoplastic elastomers consisting of triblock copolymers (MBM) with outer syndiotactic poly(methyl methacrylate) (sPMMA) blocks associated to an inner polybutadiene (PBD) block have been modified by stereocomplexation with isotactic PMMA (iPMMA) at a constant 2/1 sPMMA/iPMMA (or s/i) mixing ratio. Toluene cast films of these stereocomplexes have been studied by thermal analysis as a function of molecular weight of the sPMMA blocks and the iPMMA homopolymer. Although the melting temperature of the stereocomplex (Tm) is independent of molecular weight of the sPMMA blocks ( sPMMA) in the studied range from 7000 to 46 000, the melting enthalpy increases with increasing sPMMA. This effect is, however, erased by the sample annealing at 140°C for 15 h, and a melting enthalpy of cα. 33 J/g total PMMA is then observed whatever the copolymer composition. One melting endotherm is observed in case of low sPMMA. although two melting endotherms are reported for higher sPMMA depending, however, on the heating rate. Two endotherms are indeed observed at small sPMMA as the heating rate is low. Molecular weight of iPMMA has no significant effect on either the melting temperature or the melting enthalpy of the stereocomplexes. Dynamic mechanical analysis has confirmed the phase separation of the complexed triblock copolymers. At constant molecular weight of PBD and iPMMA, stereocomplexation increases the tensile strength of MBM copolymers containing small sPMMA blocks, whereas the opposite effect is observed for longer sPMMA blocks. When the same MBM copolymer is complexed by iPMMA, the tensile properties are independent of the molecular weight of iPMMA at least in the range from 5000 to 74 000. [less ▲]

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See detailBlends of poly(vinylidene fluoride) with polyamide 6: interfacial adhesion, morphology and mechanical properties
Liu, Zehui; Maréchal, Philippe; Jérôme, Robert ULg

in Polymer (1998), 39(10), 1779-1785

The poly(vinylidene fluoride) (PVDF)/polyamide 6 (PA6) interfacial adhesion has been measured, and morphology and mechanical properties of the binary blends have been investigated. The lap shear strength ... [more ▼]

The poly(vinylidene fluoride) (PVDF)/polyamide 6 (PA6) interfacial adhesion has been measured, and morphology and mechanical properties of the binary blends have been investigated. The lap shear strength of the PVDF/PA6 pair indicates a high interfacial adhesion, which is evidence for specific intermolecular interactions between the two polymers. Immiscibility of PVDF and PA6 has clearly been observed by transmission electron microscopy (TEM). It reflects the high propensity of each polymer to crystallize on its own and the strong hydrogen bonding that prevails in PA6. This interfacial adhesion can account for the fine phase morphology of the binary blends. Dependence of Young's modulus and yield stress on the blend composition shows a slightly negative deviation with respect to the additivity law, in contrast to elongation at break, ultimate tensile strength and impact toughness that display a positive deviation. These experimental observations have been discussed in reference to the interfacial adhesion and the change in crystallinity of the continuous phase. An optimum interfacial adhesion seems to be required for promoting a synergism in the impact resistance of these polyblends. [less ▲]

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See detailEthylene polymerization by a high activity MgCl2 supported Ti catalyst in the presence of hydrogen and/or 1-octene
Hindryckx, François; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Polymer (1998), 39(3), 621-629

This paper presents the results of slurry polymerisation of ethylene that has been initiated by an Al/Ti/Mg-alcohol supported catalyst. Special attention has been paid to the effects of hydrogen, catalyst ... [more ▼]

This paper presents the results of slurry polymerisation of ethylene that has been initiated by an Al/Ti/Mg-alcohol supported catalyst. Special attention has been paid to the effects of hydrogen, catalyst composition and addition of an α-olefin on catalyst efficiency, molecular weight, crystallinity, and physico-mechanical properties of the final polyolefin. The efficiency of this Al/Ti/Mg catalyst, molecular weight and melting temperature of the formed High Density Polyethylene (HDPE) has been found to decrease as the partial pressure of hydrogen is increased. In parallel, crystallinity and elongation at break of HDPE increase. The composition of this Al/Ti/Mg catalyst has a marked effect on catalyst efficiency, e.g. decrease in the Ti relative content results in an improved efficiency from 86 to 7942 kg PE g-l Ti h-1 as the Mg/Ti molar ratio is increased from 1 to 333. Copolymerisation with 1-octene has also been investigated. When ethylene polymerisation is carried out with this Al/Ti/Mg catalyst at a Mg/Ti ratio of 333, addition of the cr-olefin is responsible for a decrease in the polymerisation rate, which is typical of a negative 'comonomer' effect. This effect is still more pronounced in the presence of H2. Comparison with other catalytic systems has been made in order to understand the role played by the cr-olefin and/or hydrogen on the catalyst efficiency and the physico-mechanical properties of the resulting polyolefins. [less ▲]

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See detailBiodegradable and biocompatible inorganic-organic hybrid materials. 2. Dynamic mechanical properties, structure and morphology
Tian, Dong; Blacher, Silvia ULg; Dubois, Philippe ULg et al

in Polymer (1998), 39(4), 855-864

Dynamic mechanical properties, structure and morphology of tetraethoxysilane/poly(ε-caprolactone) (TEOS/ PCL) hybrid materials have been analysed by dynamic mechanical spectroscopy, small-angle X-ray ... [more ▼]

Dynamic mechanical properties, structure and morphology of tetraethoxysilane/poly(ε-caprolactone) (TEOS/ PCL) hybrid materials have been analysed by dynamic mechanical spectroscopy, small-angle X-ray scattering, transmission electron microscopy, and image analysis. The experimental observations agree with a microscopic phase separation of the two constitutive components: the organic polymer and the silica network. The effect of the PCL functional end-groups, the number of functional end-groups per PCL chain, the PCL molecular weight and content, and the curing conditions have been studied on the structure and properties of the hybrid materials. Finally, phase morphology has proved to be co-continuous, at least when the weight composition is close to 50% for each component (SiO2 and PCL), with a characteristic length between the PCL and silica phases of ca. 5 nm, as estimated by image analysis of transmission electron micrographs. [less ▲]

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See detailElectrochemistry of N-vinyl-2-pyrrolidone and a non polymerizable analogue
Calberg, Cédric ULg; Kroonen, D.; Mertens, Marc et al

in Polymer (1998), 39(1), 23-29

According to previous studies, the electropolymerization of N-vinyl-2-pyrrolidone fits a cationic mechanism with grafting of the polymer onto the platinum anode. However, this article shows that the ... [more ▼]

According to previous studies, the electropolymerization of N-vinyl-2-pyrrolidone fits a cationic mechanism with grafting of the polymer onto the platinum anode. However, this article shows that the pyrrolidone substituent of N-VP is also involved in the anodic reaction in addition to the polymerizable vinyl double bond. This additional reaction in the potential range of interest was confirmed by the electrochemical oxidation of a non polymerizable analogue of N-VP, i.e. N-methylpyrrolidone. Therefore, at least two mechanisms can contribute to the electrodeposition of a polymer film in a solvent of poly N-VP: electrografting and polymer branching and/or crosslinking by species stemming from the electrooxidation of the pyrrolidone rings. [less ▲]

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See detailMelting and crystallization of poly(vinylidene fluoride) blended with polyamide 6
Liu, Zhehui; Maréchal, Philippe; Jérôme, Robert ULg

in Polymer (1997), 38(20), 5149-5153

Melting and crystallization of poly(vinylidene fluoride) (PVDF) blended with polyamide 6 (PA6) has been studied by differential scanning calorimetry. The melting of PVDF and PA6 is observed over a small ... [more ▼]

Melting and crystallization of poly(vinylidene fluoride) (PVDF) blended with polyamide 6 (PA6) has been studied by differential scanning calorimetry. The melting of PVDF and PA6 is observed over a small temperature range, i.e. 174 to 181 degrees C and 220 to 230 degrees C, respectively, over the whole blend composition. This observation indicates that PVDF and PA6 are immiscible and do not co-crystallize, although evidence for intermolecular interactions between PVDF and PA6 has been previously reported. Crystallinity of PVDF seems to decrease on addition of the first 30 wt% PA6, although this effect is not so different from the experimental errors. Kinetics of non-isothermal crystallization of pure PVDF and PVDF blends containing 20 and 40 wt% PA6 has been investigated. The crystallization rate of PVDF is not influenced by PA6 in the temperature range 138.5-145 degrees C. At lower temperatures, it is, however, adversely affected by addition of PA6. The non-isothermal crystallization data for PVDF are fitted by the Ozawa equation in the temperature range 131-141 degrees C. The Ozawa index, or Avrami exponent, for pure PVDF decreases from 3 to 1 on decreasing temperature. This observation agrees with the nucleation of PVDF crystals which is heterogeneous, and a decrease from 3 to 1 in the growth dimension. The main effect of PA6 is to restrict the decrease of the Avrami exponent from 3 to 2 on decreasing temperature, more likely due to a slower decrease in the growth dimension. PA6 does not contribute to nucleation although it is phase separated. [less ▲]

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See detailD.m.a. and d.s.c. investigations of the β transition of poly(vinylidene fluoride)
Liu, Zhehui; Maréchal, Philippe; Jérôme, Robert ULg

in Polymer (1997), 38(19), 4925-4929

The origin of the beta transition in poly(vinylidene fluoride) (PVDF) is still a pending question. This transition has been studied by dynamic mechanical analysis (d.m.a.) and differential scanning ... [more ▼]

The origin of the beta transition in poly(vinylidene fluoride) (PVDF) is still a pending question. This transition has been studied by dynamic mechanical analysis (d.m.a.) and differential scanning calorimetry (d.s.c.) in dependence on sample annealing and dilution with epsilon-caprolactam (CPL). The beta transition temperature is increased upon annealing and thus influenced by the polymer crystallization. Upon addition of CPL, there is no systematic shift in the beta transition temperature, in contrast to the PVDF crystallinity that increases steadily. A shoulder on the low temperature side of the beta transition peak is also observed as a result of annealing. It is shifted to lower temperatures when CPL is added, consistently with a glass transition. It thus appears that the so-called beta-transition is sensitive to the amorphous material, but in a close relationship with the polymer crystallization. Comparison of the observations by d.s.c, and d.m.a. shows that the broad transition observed for the unannealed samples would result from the overlap of two transitions: the glass transition of the unconstrained amorphous phase and the glass transition of chains constrained by the crystalline phase. This situation can account for the complex dependence of the beta transition on the polymer history. [less ▲]

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