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See detailKey criteria for the design of polymeric stabilizers for aqueous titanium dioxide dispersions of high solid content
Creutz, Serge; Jérôme, Robert ULg

in e-Polymers (2001), (14), 1-9

Amphiphilic copolymers consisting of an animated hydrophobic block and a hydrophilic poly(sodium methacrylate) one have been synthesized with different structures and tested as stabilizers for aqueous ... [more ▼]

Amphiphilic copolymers consisting of an animated hydrophobic block and a hydrophilic poly(sodium methacrylate) one have been synthesized with different structures and tested as stabilizers for aqueous dispersions of alumina coated titanium dioxide (80 wt.-% solid). The dispersion stability is ruled by the strength of the anchoring of the aminated block onto the pigment and by the dynamics of the micelles formed by the copolymer. Any decrease in the anchoring strength, for example as a result of higher steric hindrance for the adsorbing block or of random rather than blocky distribution of the aminated co-units, is detrimental to the dispersion stability and makes this stability more dependent on the copolymer composition. Indeed, the position and dynamics of the unimers micelles equilibrium then control the adsorption of the copolymer on the pigment during the grinding process. [less ▲]

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See detailEffectiveness of block copolymers as stabilizers for aqueous titanium dioxide dispersions of a high solid content
Creutz, Serge; Jérôme, Robert ULg

in Progress in Organic Coatings (2000), 40(1-4), 21-29

Copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for the aqueous dispersion of titanium dioxide (80 wt.% solid ... [more ▼]

Copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for the aqueous dispersion of titanium dioxide (80 wt.% solid). The molecular composition of the block copolymers has an effect on the dispersion stability. Triblock copolymers consisting of PMANa outer blocks are unable to stabilize the dispersion. Triblock copolymers of the reverse structure form poorly stable dispersions due to at least partial particle bridging. In the case of non-blocky distribution of the DMAEMA and MANa comonomers in the chains, the stabilization capability is lost. A decrease in the anchoring strength of the diblocks has a deleterious effect on the dispersion stability. Finally, the surface coverage depends on the availability of free copolymer chains (unimers) coexisting with micelles. These trends have been confirmed in a fully formulated paint containing Cu-phthalocyanine pigment. [less ▲]

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See detailTuning of the exchange dynamics of unimers between block copolymer micelles with temperature, cosolvents, and cosurfactants
van Stam, Jan; Creutz, Serge; De Schryver, Frans C et al

in Macromolecules (2000), 33(17), 6388-6395

The dynamics of unimer exchange between aqueous micelles, formed by two amphiphilic block copolymers, i.e., poly(styrene-b-sodium methacrylate) and poly(tert-butylstyrene-b-sodium methacrylate), has been ... [more ▼]

The dynamics of unimer exchange between aqueous micelles, formed by two amphiphilic block copolymers, i.e., poly(styrene-b-sodium methacrylate) and poly(tert-butylstyrene-b-sodium methacrylate), has been investigated by steady-state fluorescence spectroscopy. The kinetics are so slow at room temperature that no exchange could be detected over several hours, while at 60 °C the exchange rate constants could be estimated. These results corroborate our previous findings that the rate is slowed down by increasing the hydrophobicity of the core. In addition to the temperature, the exchange can also be tuned by the addition of either a cosolvent or a cosurfactant. The efficiency of these additives to speed up the exchange process is related to their water solubility and their compatibility with the hydrophobic core of the micelles. The most pronounced effect on the exchange process is observed when the water solubility is low and the mixing of the additive with the hydrophobic core is favorable. [less ▲]

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See detailAggregates formed by amphoteric diblock copolymers in water
Gohy, Jean-François; Creutz, Serge; Garcia, Myriam et al

in Macromolecules (2000), 33(17), 6378-6387

The associating behavior of a series of monodisperse poly(2-(dimethylamino)ethyl methacrylate)-b-poly(methacrylic acid) (PDMAEMA-b-PMAA) ampholytic diblock copolymers has been studied in water in the ... [more ▼]

The associating behavior of a series of monodisperse poly(2-(dimethylamino)ethyl methacrylate)-b-poly(methacrylic acid) (PDMAEMA-b-PMAA) ampholytic diblock copolymers has been studied in water in the dilute regime as a function of pH and salt concentration. Dynamic light scattering (DLS) has been used to monitor the association behavior and transmission electron microscopy (TEM) to visualize the morphology of the aggregates. At and around the isoelectric point (IEP) of the ampholytic diblocks, strong electrostatic interactions occur and lead to the formation of insoluble complexes between negatively and positively charged blocks. These electrostatic interactions can be screened by the addition of salt, which leads to the partial dissolution of the material, according to Debye screening. For samples containing a major PDMAEMA block, spherical micelles are observed below the IEP. These micelles consist of a PMAA core surrounded by a water-soluble protonated PDMAEMA corona. At and above the IEP, these samples are insoluble. Spherical micelles are also formed below the IEP for samples containing a minor PDMAEMA block. These copolymers are insoluble at and around the IEP, whereas solubility is observed above the IEP with formation of aggregates of remarkable morphologies, including hollow spheres and complex compartmentalized aggregates. This aggregation is most favorable at high pH, and it cannot be accounted for only by electrostatic interaction between oppositely charged blocks. Indeed, short-range hydrophobic interaction between uncharged PDMAEMA blocks seems to play a key role in the association process. This is emphasized by quaternized poly(2-(dimethylamino)ethyl methacrylate)-b-poly(methacrylic acid) ampholytic copolymers which are carrying a permanent positive charge on the aminated monomeric units and do not form these particular aggregates. [less ▲]

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See detailEffectiveness of poly(vinylpyridine) block copolymers as stabilizers of aqueous titanium dioxide dispersions of a high solid content
Creutz, Serge; Jérôme, Robert ULg

in Langmuir (1999), 15(21), 7145-7156

Diblock copolymers of 4-vinylpyridine (4VP) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for aqueous dispersions (80 wt % solid) of alumina-coated titanium dioxide. P4VP ... [more ▼]

Diblock copolymers of 4-vinylpyridine (4VP) and sodium methacrylate (MANa) have been synthesized and tested as dispersants for aqueous dispersions (80 wt % solid) of alumina-coated titanium dioxide. P4VP is strongly anchored onto the pigment surface. The molecular composition of the block copolymers has an effect on the amount of copolymer required for imparting good stability to the slurry. Where the two parent triblock copolymers are concerned, triblocks consisting of PMANa outer blocks have a stabilizing efficiency comparable to the diblock copolymers, whereas the reverse structure is much less efficient. In the case of a nonblock distribution of 4VP and MANa in the copolymer chains, the stabilization effect is lost. Finally, the comparison of different stabilizing blocks attached to the same anchoring block confirms that the electrosteric stabilization mechanism is superior to the steric stabilization mechanism. A decrease in the anchoring strength of the diblocks has a deleterious effect on the dispersion stability. [less ▲]

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See detailProcédé pour la polymérisation radicalaire contrôlée
Creutz, Serge; Dubois, Philippe; Jérôme, Robert ULg

Patent (1998)

The invention concerns a method for making a polymer or a copolymer by radical polymerisation of at least one unsaturate monomer in the presence of a stabiliser.

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See detailTransmission and confocal fluorescence microscopy and time-resolved fluorescence spectroscopy combined with a laser trap: investigation of optically trapped block copolymer micelles
Gensch, Thomas; Hofkens, Johan; van Stam, Jan et al

in Journal of Physical Chemistry B (1998), 102(43), 8440-8451

Optical trapping was combined with transmission microscopy (TM), confocal and nonconfocal fluorescence scanning microscopy (CFSM and FSM, respectively), and confocal and nonconfocal time-resolved ... [more ▼]

Optical trapping was combined with transmission microscopy (TM), confocal and nonconfocal fluorescence scanning microscopy (CFSM and FSM, respectively), and confocal and nonconfocal time-resolved fluorescence spectroscopy (CTRFS and TRFS, respectively) to study latex particles and block copolymer micelles. Dye-labeled latex particles of various size, in polymer composite films as well as optically trapped in solution, were studied with CFSM to characterize the limits of the setup. CFSM revealed that the resolution in the x- and y-directions was near the theoretical limit, i.e., 200−250 nm. CTRFS on the labeled latex particles revealed that the decay time of the label was not influenced by the polymer matrix nor the optical trap. Poly(tert-butylstyrene-block-sodium methacrylate) micelles (diameter approximately 30−40 nm) in deuterated aqueous solutions could be optically trapped, this region of high copolymer micelle concentration being referred to as a trapped cluster. In the transmission images, trapped clusters of 1.5−2 μm diameter were detected. Fluorescence images were obtained using perylene as a fluorophore that is specifically dissolved within the block copolymer micelles. The size of the trapped cluster, estimated from TM and FSM images, increases with increasing irradiation time and power, respectively. In the TM images, the trapped cluster appears as a dark spot (low transmission) with a bright (high transmission) corona-like ring around it. The appearance of the corona is explained as a light deflection phenomenon; i.e., the trapped cluster acts as lens due to a lateral refractive index gradient. When the corona is taken into account when the diameter of the trapped clusters is calculated, a very good agreement is found between TM and FSM. Long irradiation times lead to the formation of large trapped clusters, which are stable for about 10 s, with diameters of several hundred nanometers, while, for short irradiation times, the trapped cluster is smaller and disappears within a time less than 1 s. With CFSM it could be shown that the trapped particle has a spot size of approximately 1.7 μm in the region of the IR laser focus, while the diameter extends up to 5 μm without using the confocal imaging capability. The reason for this is that the conditions for optical trapping are fulfilled not only in but also above and below the focal region. Due to the high numerical aperture, a dumbbell-like shape of the trapped cluster results. [less ▲]

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See detail4-Methoxypyridine N-Oxide: a new regulator for the controlled free radical polymerization of methyl methacrylate
Detrembleur, Christophe ULg; Lecomte, Philippe ULg; Caille, Jean-Raphaël et al

in Macromolecules (1998), 31(20), 7115-7117

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See detailMethod for controlled radical polymerisation
Jérôme, Robert ULg; Creutz, Serge; Dubois, Philippe et al

Patent (1998)

The invention concerns a method for making a polymer or a copolymer by radical polymerisation of at least one unsaturate monomer in the presence of a stabiliser whereby a stabiliser complying with general ... [more ▼]

The invention concerns a method for making a polymer or a copolymer by radical polymerisation of at least one unsaturate monomer in the presence of a stabiliser whereby a stabiliser complying with general formula (I) is used in which the substituents (Z)m, (R)n and Y can have different values. [less ▲]

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See detailMethod for controlled radical polymerization
Jérôme, Robert ULg; Creutz, Serge; Dubois, Philippe et al

Patent (1998)

The invention concerns a method for making a polymer or a copolymer by radical polymerisation of at least one unsaturate monomer in the presence of a stabiliser whereby a stabiliser complying with general ... [more ▼]

The invention concerns a method for making a polymer or a copolymer by radical polymerisation of at least one unsaturate monomer in the presence of a stabiliser whereby a stabiliser complying with general formula (I) is used in which the substituents (Z)m, (R)n and Y can have different values. [less ▲]

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See detailDynamics of poly((dimethylamino)alkyl methacrylate-block-sodium metha-crylate) micelles. Influence of hydrophobicity and molecular architecture on the exchange rate of copolymer molecules
Creutz, Serge; Van Stam, Jan; De Schrijver, Frans C et al

in Macromolecules (1998), 31(3), 681-689

The dynamic stability of the micellar aggregates formed by amphiphilic block copolymers, i.e., poly((dimethylamino)alkyl methacrylate-b-sodium methacrylate), has been investigated by steady-state ... [more ▼]

The dynamic stability of the micellar aggregates formed by amphiphilic block copolymers, i.e., poly((dimethylamino)alkyl methacrylate-b-sodium methacrylate), has been investigated by steady-state fluorescence spectroscopy and size exclusion chromatography. The dynamics of exchange of block copolymer molecules between the micelles, formed in aqueous solution, depend on a manifold of factors, e.g., alkyl substituent in the hydrophobic block, the relation between the hydrophobic and hydrophilic blocks, and the architecture of the block copolymer. All copolymers investigated show a slow unimer exchange with an exchange rate constant on the order of 10-3 s-1, with a difference of a factor of 20 between the fastest and the slowest exchange. It is possible to tune the exchange rate in a controlled way; for instance, an extension or branching of the alkyl chain slows down the exchange rate. The same effect is observed when the hydrophobic/hydrophilic balance of these copolymers is increased or when either the hydrophilic or the hydrophobic moiety of diblocks is divided into two external blocks, leading to a triblock copolymer. [less ▲]

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See detailAnionic block copolymerization of 4-vinylpyridine and tert-butyl methacrylate at "elevated" temperature : influence of various additives on the molecular parameters
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1997), 30(19), 5596-5601

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block ... [more ▼]

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block copolymerization with tert-butyl methacrylate (tBMA) has been shown to be dependent on the addition mode, highlighting the difference in reactivity between the two monomers. Moreover, the (co)solvent also strongly influences the fate of that copolymerization. Thus, the impact of various (co)solvents and additives has been investigated more thoroughly, revealing the interesting possibility of modifying the apparent relative reactivities of these two monomers. [less ▲]

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See detailLiving anionic homo- and block copolymerization of 2-(tert-butylamino) ethyl methacrylate
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Journal of Polymer Science. Part A, Polymer Chemistry (1997), 35(10), 2035-2040

Anionic polymerization of 2-(tert-butylamino)ethyl methacrylate (tBAEMA), which bears an unprotected secondary amine moiety, has been investigated in THF at -78°C. The presence of lithium chloride has ... [more ▼]

Anionic polymerization of 2-(tert-butylamino)ethyl methacrylate (tBAEMA), which bears an unprotected secondary amine moiety, has been investigated in THF at -78°C. The presence of lithium chloride has been shown to be desirable to afford narrow molecular weight distribution as well as a good agreement between theoretical and observed molecular weight. The living character of the polymerization has also been demonstrated, and the synthesis of block copolymers carried out successfully. They have been analyzed by SEC by adding a mixture of secondary and tertiary amines to the eluent (THF) so as to avoid any polymer adsorption during elution. © 1997 John Wiley [less ▲]

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See detailExchange of polymer molecules between block copolymer micelles studied by emission spectroscopy. A method for the quantification of unimer exchange rates
Creutz, Serge; van Stam, Jan; Antoun, Sayed et al

in Macromolecules (1997), 30(14), 4078-4083

Amphiphilic block copolymers, composed of poly(sodium methacrylate) (PMANa) as the water soluble sequence and poly((dimethylamino)ethyl methacrylate) (PDMAEMA) as the hydrophobic sequence, were ... [more ▼]

Amphiphilic block copolymers, composed of poly(sodium methacrylate) (PMANa) as the water soluble sequence and poly((dimethylamino)ethyl methacrylate) (PDMAEMA) as the hydrophobic sequence, were anionically synthesized. Due to their amphiphilic character, these polymers aggregate into micelles in aqueous solutions. Of particular interest is the possibility of exchange of free chains, called unimers, between micelles and the bulk and the quantification of the exchange rate. The exchange of unimers between the micellar aggregates was determined spectroscopically. A donor molecule, naphthalene, was covalently bound to the hydrophobic blocks of the copolymers, while the acceptor, pyrene, was dissolved in aggregates built up from an identical, but unlabeled, copolymer. The energy transfer from an excited donor to a ground-state acceptor, with subsequent emission from the acceptor, was used to follow the migration of donor-labeled chains into micelles containing the dissolved acceptor. These data were analyzed according to a kinetic model, and the respective kinetic parameters could be determined. The influence of the relative composition of the block copolymer on the exchange rate was investigated to illustrate the usability of the kinetic model. While keeping the relative amount of comonomers as well as the molecular weights constant, the molecular architecture was also studied: hence the diblock (PDMAEMA-b-PMANa) and the corresponding triblocks (PDMAEMA-b-PMANa-b-PDMAEMA) and (PMANa-b-PDMAEMA-b-PMANa) were investigated. [less ▲]

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See detailLiving Anionic Homopolymerization and Block Copolymerization of 4-Vinylpyridine at "Elevated" Temperature and Its Characterization by Size Exclusion Chromatography
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1997), 30(1), 1-5

The anionic polymerization of 4-vinylpyridine (4VP) has been investigated in 9/1 pyridine/THF at 0 °C. After characterization of the living character of 4VP polymerization, its copolymerization with tert ... [more ▼]

The anionic polymerization of 4-vinylpyridine (4VP) has been investigated in 9/1 pyridine/THF at 0 °C. After characterization of the living character of 4VP polymerization, its copolymerization with tert-butyl methacrylate (tBMA) has been carried out also successfully. Their relative reactivity ratios have been determined. Solvent composition as well as temperature have been varied in order to evaluate their influence on the final molecular characteristics of the polymers. Finally, a new SEC methodology in 8/1/1 N,N-dimethylformamide/triethylamine/pyridine has been developed. [less ▲]

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See detailLiving Anionic Homopolymerization and Block Copolymerization of (Dimethylamino)ethyl Methacrylate
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1997), 30(1), 6-9

Anionic polymerization of (dimethylamino)ethyl methacrylate (DMAEMA) has been investigated in THF at -78°C. The presence of lithium chloride has been shown to be desirable in order to afford a narrow ... [more ▼]

Anionic polymerization of (dimethylamino)ethyl methacrylate (DMAEMA) has been investigated in THF at -78°C. The presence of lithium chloride has been shown to be desirable in order to afford a narrow molecular weight distribution as well as a good agreement between theoretical and observed molecular weight. The living character of the polymerization has been demonstrated. Thus the synthesis of block copolymers, some of them unattainable by GTP, has been carried out successfully. Finally, the anionic polymerization of mixtures of tert-butyl methacrylate (tBMA) and DMAEMA has been considered and their relative reactivity ratio estimated. The easy quaternization of (dimethylamino)ethyl methacrylate affords amphiphilic water-soluble copolymers displaying interesting characteristics as polymeric dispersants and surfactants. [less ▲]

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See detailOrganisation and shape of micellar solution of block copolymers
Gaspard, Jean-Pierre ULg; Creutz, Serge; Jérôme, Robert ULg et al

in Physica B: Condensed Matter (1997), 234-236

Diblock copolymers of polymethacrylic acid sodium salt, forming the hair, and styrene derivatives have been studied in aqueous solutions by SANS and by SAXS. The influence of both the chemical nature and ... [more ▼]

Diblock copolymers of polymethacrylic acid sodium salt, forming the hair, and styrene derivatives have been studied in aqueous solutions by SANS and by SAXS. The influence of both the chemical nature and the length of the hydrophobic block on the size and shape of micelles have been investigated. The micellar core size is in agreement with the theoretical evaluation for copolymers with a short hydrophobic sequence. In contrast, in case of larger hydrophobic blocks, the measured size is incompatible with a star-like model. Various hypotheses are presented for the latter. [less ▲]

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