Estudo da transição colapsado-estendido em soluções de polieletrólitos flexíveis

Abstract

In this work, we propose a simple model to describe the colapsed-extended transition observed experimentally in solutions containing polyelectrolytes, ionic surfactants and salts. The model uses the Debye-H¨uckel, Bjerrum, Manning and Flory theories, with the hydrophobic interaction treated in the framework of the van der Walls theory. We study the conformation of the complexes formed by negatively charged polyelectrolytes and cationic surfactants. We found that the complex stays in a colapsed state, as a result of the electrostatic interaction and the hydrofobic effect between the associated surfactant molecules. With the addition of anionic surfactant, we observe an abrupt transition to an extended conformation, as a result of the hydrophobic interaction present in our model. Finally, we propose a phase diagram, relating the surfactant concentration and the hydrophobic strength with the observed complex transition.