COLL 177 |
| Q Qiu and P. Somasundaran. NSF IUCUR Center for Advanced Studies in Novel Surfactants, Columbia University, Langmuir Center for Colloids and Interfaces, New York, NY 10027 |
| Adsorption of poly(vinyl caprolactam) (PVCAP) and their binary mixtures at the silica/water interface was studied as a function of molecular weight. As expected, higher the molecular weight, higher was the adsorption on silica. The lower critical solution temperature (LCST) of these polymers was in qualitative agreement with Flory-Huggins°¦ polymer theory, with the adsorption density at the silica/water interface correlating with molecular weight as MW 0.16ƒp0.04. Interestingly, these properties of PVCAP are sensitive to the sample polydispersity. Upon mixing 85K PVCAP with 1.5K PVCAP, the adsorption of polymer mixtures on silica is composition dependent: below 10%wt. 1.5K PVCAP, both polymers adsorb to their equilibrium value; at higher content 1.5K PVCAP, it competes with 85K PVCAP and this results in a lower total adsorption than the sum of the single component adsorption, but still higher than their weight-average mean adsorption. In contrast, the phase behavior of the solution was found to be dominated exclusively by the higher molecular weight component under all conditions. Clearly the properties of PVCAP are not only affected by the apparent molecular weight of the polymer, but also its polydispersity and the reasons for this are explored with the help of electrokinetic and flocculation/dispersion results for the system. |
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Adsorption of Macromolecules at Liquid-Solid Interfaces
Division of Colloid and Surface Chemistry |