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See detailAssociation of telechelic ionomers in apolar solvents
Chassenieux, Christophe; Nicolai, Taco; Tassin, Jean-François et al

in Macromolecular Rapid Communications (2001), 22

The associative properties of well-defined halatotelechelic ionomers in an apolar solvent were studied by means of dynamic mechanical spectroscopy, small-angle X-ray scattering, as well as static and ... [more ▼]

The associative properties of well-defined halatotelechelic ionomers in an apolar solvent were studied by means of dynamic mechanical spectroscopy, small-angle X-ray scattering, as well as static and dynamic light scattering. The effect of end-functionalisation was investigated by comparing results on polystyrene (PS) and polyisoprene (PI) precursors using PS and PI of the same molar mass modified at one or both ends with sulfonate groups. The molar-mass dependence was investigated by comparing difunctionalised samples with different molar masses and the influence of the backbone by comparing polystyrene and polyisoprene. Experimental data suggest a relatively simple model for the association of this material. At low concentrations, the polymer chains organise themselves into well-defined reversed micelles, so-called flowers. Above a certain concentration C+, the flowers associate into larger aggregates according to an open association mechanism. At a critical concentration Cgel, the aggregates fill the whole space and a transient network is formed most likely by a percolation process. A semi-quantitative description of the associating process can be obtained by considering an open association mechanism properly combined with inter-particle interactions. [less ▲]

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See detailPreparation and properties of layered silicate nanocomposites based on ethylene vinyl acetate copolymers
Alexandre, Michaël ULg; Beyer, Günter; Henrist, Catherine ULg et al

in Macromolecular Rapid Communications (2001), 22(8), 643-646

(Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler ... [more ▼]

(Nano)composites based on ethylene vinyl acetate copolymers (EVA) and montmorillonite modified by various alkylammonium cations were processed by mechanical kneading. Polymer intercalation and filler exfoliation were evidenced by X-ray diffraction and transmission electron microscopy, respectively. Nano-composites tensile properties showed that Young's modulus increases significantly even at very low content of the organo-modified filler while preserving high ultimate elongation and tensile stress. The matrix thermal stability in air was increased by 40°C and, interestingly, the obtained nanocomposites present flame retardant properties. TEM micrograph of the nanocomposite based on EVA3 filled with 5 wt.-% of Mont-2CN2C18. [less ▲]

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See detailReverse atom-transfer radical polymerization at room temperature
Wang, Wenxin; Yan, Deyue; Jiang, Xuling et al

in Macromolecular Rapid Communications (2001), 22(6), 439-443

This paper aims at reporting on the living/controlled radical polymerization of methyl methacrylate initiated with the benzoyl peroxide (BPO)/CuIX (X=Br,Cl)/2,2'-bipyridine (bpy) redox system at room ... [more ▼]

This paper aims at reporting on the living/controlled radical polymerization of methyl methacrylate initiated with the benzoyl peroxide (BPO)/CuIX (X=Br,Cl)/2,2'-bipyridine (bpy) redox system at room temperature. No control is observed for the polymerization conducted in bulk and in toluene, whereas a polymer with predetermined molecular weight and rather narrow molecular weight distribution is formed in butanone. The solvent has thus a decisive effect on the reverse atom-transfer radical polymerization of methyl methacrylate initiated with the BPO/CuIX (X = Br,Cl)/bpy ternary system at 25°C. [less ▲]

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See detailUse of metallocenes in the polymerization-filling technique with production of polyolefin-based composites
Alexandre, Michaël ULg; Martin, Eric; Dubois, Philippe ULg et al

in Macromolecular Rapid Communications (2000), 21(13), 931-936

In an updated version of the polymerization-filling technique, the surface of particulate fillers has been activated by metallocenes. Homogeneously filled polyolefins have accordingly been produced by the ... [more ▼]

In an updated version of the polymerization-filling technique, the surface of particulate fillers has been activated by metallocenes. Homogeneously filled polyolefins have accordingly been produced by the in situ copolymerization of ethylene and α-olefins, e.g., 1-octene and 1,9-decadiene. Different fillers have been successfully used, including inorganic particles with either an acidic surface (kaolin, glass beads, silica) or a basic surface (magnesium hydroxide, wollastonite), graphite and nickel particles. Hydrogen has proved to be efficient in reducing the molecular weight of the produced polymers. [less ▲]

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See detailFirst example of an unsymmetrical difunctional monomer polymerizable by two living/controlled methods
Mecerreyes, David; Humes, J.; Miller, R. D. et al

in Macromolecular Rapid Communications (2000), 21(11), 779-784

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization ... [more ▼]

In this paper the synthesis and (co)polymerizations of 4-(acryloyloxy)-epsilon-caprolactone are reported. This new monomer can be polymerized in a living/controlled way by two different polymerization mechanisms: atom transfer radical polymerization (ATRP) and ring-opening polymerization (ROP). ATRP, which was carried out at 90 degrees C using NiBr2(PPh3)(2), leads to new polyacrylates containing pendant caprolactone functionalities with controlled molecular weights and narrow polydispersities (M-w/M(p)similar to 1.1). Alternatively, ROP of this functional epsilon-caprolactone bearing a pendant acrylate functionality leads to new poly(4-(acryloyloxy) caprolactone) as well as random copolymers when epsilon-caprolactone and L,L-lactide are added as comonomers. The (co)polymerizations were carried out using either (Al((OPr)-Pr-i)(3) in toluene at 25 degrees C or Sn(Oct)(2) as a catalyst at 110 degrees C producing (co)polymers with controlled molecular weights and narrow polydispersities (M-w/M(n)similar to 1.2). As a potential application, the introduction of acrylate pendant groups into the polyesters facilitated the preparation of cross-linked biodegradable materials either thermally or by irradiation with ultraviolet light radical curing. [less ▲]

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See detailSubstituent effect in anionic polymerization of β-lactones initiated by alkali metal alkoxides
Kurcok, Piotr; Matuszowicz, Andrzej; Jedlinski, Zbigniew et al

in Macromolecular Rapid Communications (1995), 16(7), 513-519

The influence of methyl substituent on the mechanism of the ring-opening polymerization of -lactones initiated by alkali metal alkoxides is discussed. Attention has been paid to the effect of the ... [more ▼]

The influence of methyl substituent on the mechanism of the ring-opening polymerization of -lactones initiated by alkali metal alkoxides is discussed. Attention has been paid to the effect of the substituent position in the monomer molecule on the ring-opening mechanism, the 3,3-dimethyl-2-oxetanone (pivalolactone), 4-methyl-2-oxetanone (beta-butyrolactone) and 2-oxetanone (beta-propiolactone) being chosen as model monomers. Moreover, it was found unexpectedly that in the case of pivalolactone polymerization, besides open-chain polymers, cyclic oligomers are produced. [less ▲]

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