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  • 1
    Electronic Resource
    Electronic Resource
    Importance of the texture of the resin in crown ether supported catalysis (1985)
    Springer
    Polymer bulletin 13 (1985), S. 185-192 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The influence of non macroporous and macroporous supports on a test reaction is studied. t-BuOH reacts with tetra O-acetyl bromoglucose in presence of silver nitrate and a supported crown ether. Two reaction products are formed. Yield and selectivity are affected by the morphology of the support. The selectivity depends on the crosslinking degree. This dependence is explained by the rigidity of the matrix and by the variation of steric hindrance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254229
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  • 2
    Electronic Resource
    Electronic Resource
    Reversible flocculation of silica suspensions by water-soluble polymers (1990)
    Springer
    Colloid & polymer science 268 (1990), S. 476-483 
    Details
    ISSN: 1435-1536
    Keywords: Silicasuspensions ; polyelectrolytes ; adsorption ; flocculation ; peptization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The possibility to concentrate, then redisperse colloidal suspensions is not only of great theoretical interest, but is also relevant to the industrial process of solid-liquid separation, which must often be followed by a redispersion stage. Up to now, these consecutive operations were unrealizable in the presence of polymers, since flocculation and adsorption were generally considered irreversible in this case. Previous studies have pointed out the occurrence of two main flocculation mechanisms: charge neutralization and interparticle bridging. The use of copolymers makes it possible to take into account these two different mechanisms together. Using this fact we prepared new copolymers of acrylamide with N-vinylimidazole via radical polymerization and characterized them by light scattering, viscometry, potentiometric titrations, and UV studies. One peculiarity of the chosen system is its dependence on pH: actually the degree of neutralization of such cationic polyelectrolytes does vary with pH, especially near the pK value. This paper shows that these copolymers may induce reversible flocculation of negatively charged suspensions, e.g., silica suspensions, by simple pH adjustment. Performances of the system were followed by various physico-chemical methods. The observed results are explained in terms of flocculation mechanisms as a function of pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01411007
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  • 3
    Electronic Resource
    Electronic Resource
    Rheological behavior of moderately concentrated silica suspensions in the presence of adsorbed poly(ethylene oxide) (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 196-203 
    Details
    ISSN: 1435-1536
    Keywords: Colloid ; polymer ; adsorption ; rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Adsorption and flocculation properties have been investigated for a well-characterized aqueous system of precipitated nanometric silicabeads in the presence of a high molecular-weight poly(ethylene oxide). Particular attention was given to the evolution of these properties with increasing concentration. In addition, the corresponding consequences on the rheological behavior in the homogeneous domains of the phase diagram of the systems were studied. Important rheological effects can actually be obtained with such systems, even at moderate values of the volume fraction of the dispersed phase (5·10−3≦Φ≦5·10−2). According to the adsorption level, the number of particles per macromolecular chain, and the free polymer equilibrium concentration, quite different phenomena were observed such as rheopectic shear-induced gelation, Newtonian flow or thixotropic shear-thinning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658848
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  • 4
    Electronic Resource
    Electronic Resource
    Coupling between polymer adsorption and colloidal particle aggregation (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 984-993 
    Details
    ISSN: 1435-1536
    Keywords: Polymer adsorption ; flocculation ; bridging ; zeta potential ; colloidal particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Studies of the adsorption of high molecular weight polymers on colloidal latex and silica particles and their subsequent flocculation were carried out. Neutral polyethylene oxide samples with both a narrow and a broad molecular weight distribution were used together with low charged cationic copolymers. The influence of the particle concentration and polymer dose on the flocculation were systematically investigated under quiescent conditions. Equilibrium bridging only occurred with polyelectrolyte, even in very dilute suspensions, at high particle coverage. In contrast to this, non-equilibrium bridging occurred with both neutral polymer and polyelectrolytes but only for more concentrated suspensions and small amounts of adsorbed polymer. Polymer adsorption in dilute suspensions, which did not show particle aggregation was measured an electrophoretic technique. In more concentrated suspensions, where flocculation takes place, we found that aggregation prevents further polymer adsorption and induces both an excluded volume and a surface effect. The consequences on the shape of the isotherms differ according to the aggregation mechanism. A significant decrease of the amount, Γ, of adsorbed polymer is observed with non-equilibrium bridging. When both mechanisms simultaneously contribute to the aggregation, the value of Γ depends on their relative importance. In the intermediate range of copolymer dose their respective contributions are critically sensitive to the details of the mixing step and stirring, leading to non reproducible experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00660377
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  • 5
    Electronic Resource
    Electronic Resource
    Viscometric behaviour of hydrophobically modified poly(sodium acrylate) (1988)
    Springer
    Polymer bulletin 20 (1988), S. 577-582 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Hydrophobically associating poly(acrylic acid) was obtained by reaction of a small amount of octadecylamine on the carboxyl groups of the polymer. In pure water, this modified polymer exhibits a very high thickening power. By increasing the ionic strength of the aqueous solution a strong viscosity increase can be obtained instead of the decrease classically observed with polyelectrolytes. For instance, in 1% NaCl the modified poly(sodium acrylate) is of several orders of magnitude more viscous than the precursor polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00263675
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  • 6
    Electronic Resource
    Electronic Resource
    Interactions of hydrophobically modified poly(sodium acrylate) with globular proteins (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 777-781 
    Details
    ISSN: 1435-1536
    Keywords: Poly(acrylic acid) ; hydrophobically modified polymer ; globular protein ; interaction ; rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The association of a series of hydrophobically modified poly(sodium acrylate) (HMPA) with lysozyme, a cationic globular protein, or with bovine serum albumin (BSA), an anionic globular protein, was investigated at pH=9 by rheology and to a lesser extent by steady-state fluorescence spectroscopy. Under suitable concentration conditions, this association leads to a drastic viscosity enhancement which is improved when the polymer hydrophobicity is increased. A mechanism is proposed: the hydrophobic regions of the globular proteins interact strongly with the alkyl groups of one or more polymer chains. In the later case, the macromolecules are crosslinked via the proteins, which leads to viscosity enhancement and even gelation. Analogies and differences between these systems and surfactant/HMPA systems previously studied in our laboratory are emphasized and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658756
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  • 7
    Electronic Resource
    Electronic Resource
    Gels of amphiphilic polyelectrolyte derivatives of poly(vinyl benzyl chloride) (1997)
    Springer
    Polymer bulletin 39 (1997), S. 741-746 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. In this paper, we present some preliminary results on the phase behaviour of amphiphilic polyelectrolytes, derivatives of poly(vinyl benzyl chloride). The phase diagram of these copolymers contains, depending on the amount of amphiphilic units and on the polymer concentration, five different domains: an isotropic liquid and isotropic gel, a birefringent gel, a gel birefringent under stirring and a demixed gel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002890050211
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  • 8
    Electronic Resource
    Electronic Resource
    Aqueous solution behavior of new thermoassociative polymers (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1163-1173 
    Details
    ISSN: 1435-1536
    Keywords: Thermothickening ; associative polymers ; lower critical solution temperature ; shear-thinning behavior ; fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new kind of water-soluble polymer was obtained by grafting side chains, characterized by a phase separation on heating (Lower Critical Solution Temperature LCST), on a hydrosoluble backbone. For semidilute solutions, the side chains associate as the temperature exceeds a critical temperature (T ass), which is close to their LCST. Microdomains are formed which act like physical crosslinking units between the main chains, and an increase in the aqueous solution viscosity is observed. Systems based on 2-Acrylamido-2-methyl propane sulfonic acid (AMPS) backbone and polyethylene oxide (PEO) side chains were developed. Their rheological behavior in both dilute and semi-dilute states was studied by varying differents parameters such as polymer and salt concentrations, grafting ratio, etc. Fluorescence measurements indicate the formation of hydrophobic microdomains on heating, in agreement with the thickening properties of the solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653085
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of adsorbed polymers on the removal of mineral particles from a planar surface (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 352-363 
    Details
    ISSN: 1435-1536
    Keywords: Key words Particle adhesion ; polymer adsorption ; flocculation ; zeta potential polyelectrolyte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Experimental results on the role of adsorbed polymers on the particle adhesion are presented. Both Brownian (silica particles) and non-Brownian (glass beads) particles were used. The particles were deposited onto the internal surface of a glass parallelepiped cell, and then submitted to increasing laminar flow rates. The pH and the ionic strength of the electrolytes were fixed. The adhesive force was related to the hydrodynamic force required to dislodge 50% of the initially attached beads. We found that high molecular weight PEO had little effect on the adhesion of small silica beads due to the low affinity of the polymer for silica or glass surfaces. On the contrary, PEO greatly enhanced the adhesion of bigger glass beads forced to deposit on the capillary surface because of gravity. The increase was all the more pronounced as the molecular weight of the polymer was high. The effect of high molecular weight cationic copolymers on the adhesion of silica particles was drastic. The maximal force (1500 pN) applied by the device could not enable any particle detachment even using polymers of low cationicity rate (5%), showing the efficiency of electrostatic attractions. When copolymers were adsorbed on both surfaces (particles and plane), the adhesive force exhibited a maximum at intermediate coverage of particles. This optimum was related to the optimum flocculation concentration classically observed in flocculation of suspensions by polymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050092
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  • 10
    Electronic Resource
    Electronic Resource
    Emulsions stabilized with hydrophobically modified poly(acrylic acid) (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 228-238 
    Details
    ISSN: 1435-1536
    Keywords: Emulsion ; amphiphilic polymer ; associative polymerstability ; rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Hydrophobically Modified (with alkylamide chain) linear Poly(acrylic acid) Sodium Salt (HMPAANa) of various degree of grafting (τ) and alkyl chain length (n) were synthesized and used as emulsifiers ofn-dodecane/water (NaNO3 10−3M) system. Stability and flow properties of the resultingn-dodecane in water emulsions (dispersed phase volume fraction=0.5) were investigated as a function ofτ (τ=0 to 10% in mol),n (n=12, 18) and polymer concentration (0–10%). It was clearly shown that viscosification (via an associative mechanism of HMPAANa) of the external phase of emulsions is a key factor to explain dispersions breakdown. However, a complete description of the phenomenon could not be achieved without considering the adsorption of the polymer at the liquid-liquid interface which depends closely onτ andn. More generally, the behavior of emulsions was found to be described adequately by the degree of hydrophobicity of HMPAANa's using a simple model conjugating the effects ofτ andn. As a matter of fact, the model was also found to provide a satisfactory description of HMPAANa's aqueous solutions as well, so that a good picture of emulsions properties can be deduced from the polymer behavior in water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188956
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