Effect of the Ionic Strength on Collapse Transition in Star‐like Polyelectrolytes

Abstract

AbstractWe present an analytical theory describing intramolecular conformational transition in a star‐shaped polyelectrolyte (PE) molecule induced by a decrease in the solvent strength or/and increase in the ionic strength in the solution. We apply a mean‐field Flory‐type analysis in a box‐like approximation, that is we assume fairly uniform distribution of densities of charged monomer units and all mobile ions (co‐ and counterions) in the intra‐molecular volume of the star. We demonstrate that depending on the number of branches, fraction of charged monomers in the star and the ionic strength of the solution different scenario of the collapse transition may take place. At high ionic strength or low degree of ionization collapse transition occurs continuously resembling the collapse of a neutral polymer star.1 On the contrary, at low ionic strength and high degree of ionization collapse transition features first order phase transition, that is, occurs discontinuously and involves coexistence of collapsed and stretched states.