Multiple interactions between molecular and supramolecular ordering

We report studies of the interplay among processes of molecular conformational changes, spinodal demixing of the solution, and molecular crosslinking involved in the physical gelation of a biopolysaccharide-water system. Multiple interactions and kinetic competition among these processes were studied under largely different absolute and relative values of their individual rates by appropriate choices of the quenching temperature at constant polymer concentration. Quenching temperature strongly affects the rate of growth but not the final value of the fractal dimension of the gel. Kinetic competition plays a central role in determining the find conformation of individual molecules and the structure and properties of the final gel. This behavior highlights the frustrated nature of the system, and the need of bringing kinetics sharply into focus in gelation theories. General aspects of the present findings and, specifically, the interplay of molecular conformation changes, solution demixing, and molecular crosslinking extend the relevance of these studies to the fast growing field of amyloid condensation and Prion diseases. [S1063-651X(99)10202-2].