ABSTRACT
This chapter provides an overview is given of the formulation components of Microemulsions (MEs), selected methods for the physicochemical characterization of MEs, and current developments in the field of cutaneous application. MEs often contain cosolvents to increase the solubility of the drug and to stabilize the dispersed phase. Combinations of various complementary techniques have been used to fully characterize MEs. The physicochemical characterization of MEs include phase stability and phase behavior, microstructure, dimension, shape, surface features, local molecular arrangements, interactions, and dynamics. Optical isotropy is one important feature of MEs. Unlike lamellar or hexagonal liquid crystals, isotropic structures do not cause birefringence between crossed polarizers. Freeze fracture electron microscopy (FFEM) is a method to visualize the microstructure of colloidal systems, mainly the size and shape of the ME droplets. Determination of rheological behavior and viscosity of MEs can be used to obtain different kinds of information.
