Ion Transport and Electrical Conductivity in Heterogeneous Systems: The Case of Microemulsions

Ion Transport and Electrical Conductivity in Heterogeneous Systems: The Case of Microemulsions FEDERICO BORDI Sezione di Fisica Medica, Dipartimento di Medicina Interna, Universita di Roma “Tor Vergata,” and Istituto Nazionale Fisica della Materia, Unita di Roma 1., Rome, Italy

CESARE CAMETTI Dipartimento di Fisica, Universita di Roma “La Sapienza,” and Istituto Nazionale Fisica della Materia, Unita di Roma 1., Rome, Italy

I. Introduction 541 II. Electrical Conductivity of Typical Colloidal Aqueous Suspensions 543

III. Electrical Conductivity of Typical Microemulsion Systems 546 IV. Conclusions 561

References 562

I. INTRODUCTION

Of the many physical or physicochemical methods that can be used to study colloidal systems, including heterogeneous systems, solid-liquid dispersions, complex fluids, and polyelectrolyte and macromolecular solutions, those involving electrical properties have been prominent. The origin of this specificity lies in the existence of charges at the interfaces disjoining the different media of the dispersed system that lead to intraand intermolecular interactions that may be stronger and of much longer range than in the case of uncharged interfaces, determining the behavior, at the macroscopic level, of the whole system.