| Abstract
| - The rheological behavior of concentrated dispersions of sterically stabilized lamellar droplets has beenstudied as a function of the molecular weight and of the amount of adsorbed hydrophobically endcappedpoly(sodium acrylate)s. The chemical compositions of the samples are identical to those described before.Despite the polydispersity of the sample, scaling laws and equations that are well established in therheology of monodisperse colloidal suspensions can be successfully applied. Although the amount of addedstabilizing polymer at constant molecular weight hardly influences the elastic modulus (G‘) as a functionof (core) volume fraction of lamellar droplets (φlam), increasing the polymer molecular weight at constantgrafting density results in a pronounced increase of the elastic modulus. The ratio of particle radius toadsorbed layer thickness (R/Δ) decreases with molecular weight, thereby increasing the effective volumefraction. A peculiar effect occurs if the polymer molecular weight drops below 1000. Polymer moleculespenetrate into the lamellar droplets, and φlam is increased (at constant surfactant concentration). Thisso-called “building-in” effect can be used to thicken lamellar dispersions. Thickening can also be inducedby addition of “bridging polymers”, which carry multiple hydrophobic anchors, linking several droplets.Concomitant adverse effects of bridging flocculation can be counteracted by admixing of hydrophobicallyendcapped polymers; the resulting dispersions are characterized by enhanced shear-thinning behaviorand good physical stability.
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