| Abstract
| - Kinetics as well as the evolution of the agarose gel topology is discussed, and the agarose gelation mechanismis identified. Aqueous high melting (HM) agarose solution (0.5% w/v) is used as the model system. It isfound that the gelation process can be clearly divided into three stages: induction stage, gelation stage, andpseudoequilibrium stage. The induction stage of the gelation mechanism is identified using an advancedrheological expansion system (ARES, Rheometric Scientific). When a quench rate as large as 30 deg C/minis applied, gelation seems to occur through a nucleation and growth mechanism with a well-defined inductiontime (time required for the formation of the critical nuclei which enable further growth). The relationshipbetween the induction time and the driving force which is determined by the final setting temperature followsthe 3D nucleation model. A schematic representation of the three stages of the gelation mechanism is givenbased on turbidity and rheological measurements. Aggregation of agarose chains is promoted in the polymer-rich phase and this effect is evident from the increasing mass/length ratio of the fiber bundles upon gelation.Continuously increasing pore size during gelation may be attributed to the coagulation of the local polymer-rich phase in order to achieve the global minimum of the free energy of the gelling system. The gel pore sizedetermined using turbidity measurements has been verified by electrophoretic mobility measurements.
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