| Autor: |
Hansch M; Universität Paderborn, Physikalische Chemie, D-33098 Paderborn, Germany., Hämisch B; Universität Paderborn, Physikalische Chemie, D-33098 Paderborn, Germany., Schweins R; Large Scale Structures Group (LSS), ILL-Institut Laue-Langevin, F-38000 Grenoble, France., Prévost S; Complex Systems and Biomedical Sciences Group (CBS), ESRF-The European Synchrotron, F-38000 Grenoble, France., Huber K; Universität Paderborn, Physikalische Chemie, D-33098 Paderborn, Germany. |
| Abstrakt: |
The dilute solution behavior of sodium poly(styrene sulfonate) is studied in the presence of trivalent Al 3+ and bivalent Ba 2+ cations at various levels of excess NaCl. The study evaluates the phase behavior and the morphology of the polyelectrolyte chains with increasing extent of decoration with the Al 3+ and Ba 2+ cations and analyses the effect of temperature on these decorated chains. The phase behavior is presented in the form of the cation concentration versus the respective poly(styrene sulfonate) concentration, recorded at the onset of precipitation. Whereas poly(styrene sulfonate) with Al 3+ exhibits a linear phase boundary, denoted as the "threshold line," which increases with increasing poly(styrene sulfonate) concentration, Ba 2+ cations show a threshold line which is independent of the poly(styrene sulfonate) concentration. An additional re-entrant phase, at considerably higher cation content than those of the threshold lines, is observed with Al 3+ cations but not with Ba 2+ cations. The threshold line and the re-entrant phase boundary form parts of the liquid-liquid phase boundary observed at the limit of low polymer concentration. The dimensions of the polyelectrolyte chains shrink considerably while approaching the respective threshold lines on increase of the Al 3+ and Ba 2+ cation content. However, subtle differences occur between the morphological transformation induced by Al 3+ and Ba 2+ . Most strikingly, coils decorated with Al 3+ respond very differently to temperature variations than coils decorated with Ba 2+ do. As the temperature increases, the poly(styrene sulfonate) chains decrease their size in the presence of Al 3+ cations but increase in size in the presence of Ba 2+ cations. |
