INTERMOLECULAR ASSOCIATION OF AMPHIPATHIC POLYELECTROLYTES IN AQUEOUS SOLUTIONS
Ríos, Hernán E.
Urzúa, Marcela D.
Vargas, Víctor A.
The intermolecular association of amphipathic polyelectrolytes is studied using fluorescence and conductivity methods. This type of interaction is evidenced by the decrease in the average distances between charges as the polyelectrolyte side chain increases in length. This modify the dissociation degree and consequently, the linear charge density parameter. These distances were calculated with the Manning counterion condensation theory for the conductivity of polyelectrolyte solutions. The determination of the ratio I1/I3 of the fluorescence bands of pyrene with polymer content reveals the formation of hydrophobic microdomains at very low concentrations, smaller than the required concentration to produce a significant change in the average distances between charges. These distances and also the I1/I3 ratio vary with polymer concentration and their values were dependent on the size of the side chain in the polyelectrolyte. Finally, the experimental behavior of the solution viscosity and electrical conductivity of polyelectrolytes, which increase drastically with dilution, can be explained as a continuous change in the average distances between charges which produce conformational changes.