Eur. Phys. J. E 6, 163-168 (2001)

Rayleigh instability of charged droplets in the presence of counterions

M. Deserno

Department of Chemistry and Biochemistry, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095-1569, USA

markus@chem.ucla.edu

(Received 30 August 2001)

Abstract
The classical instability of a charged spherical droplet is reconsidered in the presence of counterions. An ensemble of such droplets is studied within a simplified cell model. Screening of the electric field by the counterions is found to increase the equilibrium droplet size. Furthermore, if the ions can enter the droplet, a first-order phase transition occurs upon increasing Bjerrum length, surface tension or droplet density, leading to a phase separation. Simple scaling properties of the free energy give the shape of the phase boundary and show the system to be scale-invariant there. Pearl-necklace structures of hydrophobic polyelectrolytes are discussed as an application.

PACS
68.03.Cd - Surface tension and related phenomena.
36.20.Ey - Conformation (statistics and dynamics).
82.35.Rs - Polyelectrolytes.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001