Philippe Mongondry

Publications

• Rheology of highly concentrated anionic surfactants

  Mongondry, Philippe, Macosko, Christopher, Moaddel, Teanoosh

  Rheologica Acta. 01/2006; 45:891-898.

  Abstract Surfactant solution flow behavior is of great importance to both the chemical and consumer product industries. Most studies on the flow behavior of surfactant solutions, however, have focused on the dilute regime. Seldom reported is rheology in the highly concentrated regime where typically... [more] Abstract Surfactant solution flow behavior is of great importance to both the chemical and consumer product industries. Most studies on the flow behavior of surfactant solutions, however, have focused on the dilute regime. Seldom reported is rheology in the highly concentrated regime where typically these surfactants are processed and delivered. First, we present here the phase diagram for the ternary system: water and two anionic surfactants (sodium salt of lauric and oleic acid) at different temperatures. Then, we present both linear viscoelastic and steady shear flow results in the high (70 to 90%) surfactant regime. We find that high values of the shear modulus are directly dependent on the quantity of surfactant crystals and that the formation of a lamellar liquid crystal phase at 45C affects both modulus and flow of the system. Lamellar crystals create a stiff network resulting in wall slip at large shear strain. Using serrated plates removes slip at the wall and we find a shear rate where microfractures localize in a preferential plane and the material flows. This behavior is reversible.
• 3.02

  Impact points

  Revised state diagram of Laponite dispersions.

  Philippe Mongondry, Jean François Tassin, Taco Nicolai

  Journal of colloid and interface science. 04/2005; 283(2):397-405.

  We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (C(s)), based on simple observation and light-scattering measurements. At low C or high C(s) the dispersions separate into two d... [more] We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (C(s)), based on simple observation and light-scattering measurements. At low C or high C(s) the dispersions separate into two domains due to sedimentation of Laponite aggregates, while at high C and low C(s) they form homogeneous gels that do not flow upon tube reversal. The aggregation rate and the structure factor of the Laponite dispersions is determined with light scattering as a function of C and C(s). We discuss in detail the controversy on the origin of gelation of Laponite dispersions in the absence of added salt. We argue that aggregation rather than glass formation causes gelation.
• 3.02

  Impact points

  Influence of pyrophosphate or polyethylene oxide on the aggregation and gelation of aqueous laponite dispersions.

  Philippe Mongondry, Taco Nicolai, Jean François Tassin

  Journal of colloid and interface science. 08/2004; 275(1):191-6.

  The influence of pyrophosphate or polyethylene oxide (PEO) on the aggregation and gelation of dispersions of model disklike clay particles (Laponite) is studied using light scattering and rheology. Pyrophosphate adsorbs onto the positively charged rim and inhibits bond formation between the rim and ... [more] The influence of pyrophosphate or polyethylene oxide (PEO) on the aggregation and gelation of dispersions of model disklike clay particles (Laponite) is studied using light scattering and rheology. Pyrophosphate adsorbs onto the positively charged rim and inhibits bond formation between the rim and the negatively charged faces of the particles. At low concentrations of pyrophosphate the aggregation of Laponite is only retarded, without significant modification of the structure of the aggregates and gels. The decrease of the aggregation rate can be explained by an increase of the energy barrier to the formation of bonds in proportion to the pyrophosphate concentration. Addition of a large amount of pyrophosphate leads to the breakup of Laponite aggregates and gels. PEO adsorbs onto the Laponite particles and inhibits aggregation by steric hindrance. The reduction of the aggregation rate depends on the molar mass and is maximal at about 1000 g/mol. Higher molar mass PEO bridges between the particles and leads to the formation of clusters or a weak gel immediately after mixture.

• Structure et comportements rhéologiques des suspensions aqueuses de Laponite en présence de plusieurs additifs.

  Dr. Philippe Mongodnry

  06/2003

  Degree: Ph.D in physics and Chemistry

  Supervisor: Pr. Jean Francois Tassin

• Mild Synthesis of Amino-Poly(ethylene glycol)s. Application to Steric Stabilization of Clays

  Mongondry, Philippe, Bonnans-Plaisance, Chantal, Jean, Martine, Tassin, Jean François

  Macromolecular Rapid Communications. 01/2003; 24:681-685.

  The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido-PEGs gave the amino compounds in high yields. Quaternization of... [more] The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido-PEGs gave the amino compounds in high yields. Quaternization of the amino groups leads to hydrophilic polymer chains bearing a positive charge on one or two ends, depending on the chosen PEG. Such products can be used to protect sterically, negatively charged particles such as clays.

• Revised state diagram of Laponite dispersions

  Philippe Mongondry, Jean François Tassin, Taco Nicolai

  Journal of Colloid and Interface Science.

  We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (Cs), based on simple observation and light-scattering measurements. At low C or high Cs the dispersions separate into two domai... [more] We propose a state diagram of charged disk-like mineral particle (Laponite) dispersions as a function of the Laponite concentration (C) and the concentration of added salt (Cs), based on simple observation and light-scattering measurements. At low C or high Cs the dispersions separate into two domains due to sedimentation of Laponite aggregates, while at high C and low Cs they form homogeneous gels that do not flow upon tube reversal. The aggregation rate and the structure factor of the Laponite dispersions is determined with light scattering as a function of C and Cs. We discuss in detail the controversy on the origin of gelation of Laponite dispersions in the absence of added salt. We argue that aggregation rather than glass formation causes gelation.