Structure and rheological properties of model microemulsion networks filled with nanoparticles

Model microemulsion networks of oil droplets stabilized by non ionic surfactant and telechelic polymer C18-PEO(10k)-C18 have been studied for two droplet-to-polymer size ratios. The rheological properties of the networks have been measured as a function of network connectivity and can be described in terms of simple percolation laws. The network structure has been characterised by Small Angle Neutron Scattering. A Reverse Monte Carlo approach is used to demonstrate the interplay of attraction and repulsion induced by the copolymer. These model networks are then used as matrix for the incorporation of silica nanoparticles (R=10nm), individual dispersion being checked by scattering. A strong impact on the rheological properties is found for silica volume fractions up to 9%

Depletion induced sphere-cylinder transition in C12E5\mathrm{C_{12}E_5} microemulsion: A Small-Angle X-ray Scattering study

Small-angle X-ray scattering was used to study the mixture of C$_{12}$E$_5$ (pentaethylene glycol monododecyl ether)/H$_2$O/n-decane microemulsion and polyethylene glycol (PEG). The size, shape and the structure factor of the microemulsion were investigated by adding the polymer (PEG) to the mixture. Attractive depletion potential was induced between the microemulsion droplets by the non-adsorb polymer. The range and strength of the attractive potential were changed by varying the molecular weight and concentration of PEG. The forward scattering, S(0), of the spherical microemulsion, declined gradually as the polymer concentration decreased. For PEG with the molecular weight of M$_n$ = 285−315, the microemulsion morphology remained spherical, but the main peak of the structure factor moved towards a bigger q. When PEG with molecular weights of M$_n$ = 2200 and M$_n$ = 6000 were used, a shape transition from spherical to cylindrical was induced in line with increasing polymer concentration

Mixtures of n-octyl-β-D-glucoside and triethylene glycol mono-n-octyl ether: Phase behavior and micellar structure near the liquid-liquid phase boundary

The phase behavior and microstructure of aqueous mixtures of n-octyl-β-D-glucoside (C 8βG 1) and triethylene glycol mono-ra-octyl ether (C 8E 3) is presented. C 8βG 3 forms a one-phase micellar solution in water at surfactant concentrations up to 60 wt %, wheres mixtures with C 8E 3 show a liquid-liquid phase transition at low surfactant concentration. The position of this phase boundary for mixtures can be rationally shifted in the temperature-composition window by altering the ratio of the two surfactants. Small-angle neutron scattering is used to determine the size and shape of the mixed micelles and to characterize the nature of the fluctuations near the cloud point of the micellar solutions. The C 8βG 3/C 8E 3 solutions are characterized by concentration fluctuations that become progressively stronger upon approach to the liquid-liquid phase boundary, whereas micellar growth is negligible. Such observations confirm previous views of the role of the surfactant phase boundary in tuning attractive micellar interactions, which can be used effectively to change the nature and strength of interparticle interactions in colloidal dispersions. Colloidal silica particles were then added to these surfactant mixtures and were found to aggregate at conditions near the cloud point. This finding is relevant to current strategies for protein crystallization. ©2005 American Chemical Society