ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhase Diagram of Colloidal Dispersions Anisotropic Charged Particles: Equilibrium Properties, Structure, and Rheology Laponite SuspensionsA. Mourchid, A. Delville, J. Lambard, E. LeColier, P. LevitzCite this: Langmuir 1995, 11, 6, 1942–1950Publication Date (Print):June 1, 1995Publication History Published online1 May 2002Published inissue 1 June 1995https://pubs.acs.org/doi/10.1021/la00006a020https://doi.org/10.1021/la00006a020research-articleACS...

Relations between thermodynamics, structural, and mechanical properties of Laponite suspensions were recently discussed in the literature. One important issue concerning liquid/gel transition is to understand why a gel appears concomitantly with what as an incomplete nematic transition. To get some insight, we first give more extended characterization viscoelastic these near For this purpose, stress relaxation experiments are compared direct determinations modulus frequency domain. This...

We study suspensions of synthetic clay Laponite at very low ionic strength. show the existence, for these charged disk-like particles, a liquid-soft solid transition mainly driven by electrostatic repulsive interactions. Such process defines re-entrant line in phase diagram. Location this is predicted using basic arguments. The structure characterized ultra-small-angle X-ray scattering (USAXS). Soft-solid correlation peak compatible with long-range stabilization. result strongly contrasts...

The origin of the long-term gelation clay suspensions was recently questioned. We have investigated this problem by looking at chemical stability laponite solid particles as a function preparation, storage, and age suspensions. Under ambient atmosphere, ${\mathrm{Mg}}^{2+}$ is released from laponite, suggesting that carbon dioxide atmosphere promotes acidification dispersions, resulting in progressive dissolution slow increase ionic strength. These factors induce sol-gel transition, leading...

The properties of free carriers photogenerated in the extended states hydrogenated amorphous silicon have been investigated using techniques femtosecond time-resolved spectroscopy. optical susceptibility can be described by a Drude model with relaxation time shorter than 1 fs. This seems to remain constant for various experimental situations. It implies very small mobility (∼ 6 cm2/V s) states. hot thermalize quickly edge emission phonons. thermalization rate is found ≥ eV/ps. In addition,...

We present static light scattering results for Laponite suspensions. Analyzing our data using the Zimm technique, we measure a second virial coefficient of 6.0 × 10-23 m3 at an ionic strength 10-4 M. Both agree well with recent theories and computations thermodynamics hard disks. Our support conclusion that classical Onsager result underestimates repulsive contribution in discotic systems. also neutron very low q which conclusively confirm existence large-scale structure gels above...

The thermodynamical properties, structure and rheology of laponite dispersions have been studied as a function solid fraction ionic strength. undergo transition from Newtonian liquid to viscoelastic without phase separation. increase the strength shifts lower diagram has constructed for onset like behaviour. This sol–gel line coincides with appearance singularity in equation state determined by osmotic pressure measurements. Analysis transmission electron microscopy (TEM) small-angle X-ray...

The phase behavior and microstructure of the ternary system water/1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6))/Triton X-100 was studied as a function temperature ionic liquid (IL) mass fraction alpha. In present study, hydrophobic IL instead commonly used organic solvents such n-alkanes is used. fish-shaped region distorted at low high values alpha, whereas it symmetric intermediate With increasing extension three-phase decreases regarding surfactant concentration range,...

Small-angle neutron scattering and thermorheology techniques are used to investigate in detail the effect of laponite particles aqueous solutions poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), PEO-PPO-PEO, block copolymers concentrated regime. At high polymer concentration or temperature, micellar exhibit a phase transition from fluid crystal due crowding micelles. The addition is found disturb this transition. adsorption copolymer unimers onto large amounts describes these...

Rheology and dynamics of micellar solutions polystyrene-poly(acrylic acid) block copolymers are investigated in the jammed regime. With increasing attraction between soft spheres, both techniques capture re-entrant liquid-to-glass transition. The was also at an strength above transition branch. concentration sticky spheres this region, particle shows a remarkable extended logarithmic decay. All theoretical predictions mode coupling theory can be found our system.

The electronic and thermal contributions to photoinduced changes in the optical properties of hydrogenated amorphous silicon (a-Si:H) films can be distinguished pump-probe experiments by an appropriate choice probe wavelength. Intraband absorption decreases strongly with carrier localization.

We present small-angle neutron scattering and rheology for micellar solutions of polystyrene−poly(acrylic acid) block copolymers that can be regarded as attractive colloids. These systems form gels at high effective volume fractions (φ > 0.64) are suggestive disordered colloidal glasses. At the gel point, solution follows scaling predicted by classical percolation theory, with G' ∼ G'' ωΔ. argue this could due either to formation a percolated network or pretransitional glassy phase.

Using femtosecond optical pulses to inject a carrier density greater than ${10}^{19}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, we observe that most of the carriers disappear within few picoseconds. We show this phenomenon results from nonradiative recombination, process in which each electron-hole pair heats lattice by giving up an energy equal pump photon energy. The delay between recombination and heating is estimated be smaller 100 fs, may result very fast coupling acoustical phonons.

We report quantitative determination of the strength attraction between spherical micelles associative diblock copolymers. offer detailed characterization dilute micellar solutions by neutron and dynamic light scattering techniques viscometry, we interpret data with aid adhesive hard-sphere model. This model permits estimate stickiness parameter for varying fraction stickers on micelles. At this range exhibit, in crowded regime, rheological dynamics behavior representative both repulsive...

We investigate the microstructure of copolymer micellar solutions with embedded laponite colloidal particles. The exhibit microscopic confinement coated nanoparticles triggered by increasing temperature above gelation temperature. is pluronic which self-assembles into well-defined nanostructured arrays. These self-assembly properties are governed copolymer–solvent interaction through In presence nanoparticles, a large amount unimers adsorb onto laponite. Above pure micelles in solution,...

We investigate the rheological properties of copolymer-nanoparticle aqueous solutions and their connection to thermodynamic structural behavior. The samples are formed poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer micellar with embedded anisotropic colloidal laponite nanoparticles. concentrated exhibit a temperature induced phase transition from fluid crystal. Addition nanoparticles is found promote formation polycrystallized micrograins, above...

We investigate the structure of polystyrene-b-poly(acrylic acid, sodium salt) copolymer in aqueous solutions. offer detailed characterization micellar solutions by scattering techniques and show that they form hexagonal-packed cylinders. The micelles follow swelling law expected for cylinders, upon addition water, down to a concentration threshold below which distance cylinder-cylinder remains constant. results suggest cylinders are aggregated. It is proposed this association cause unusual...