Chapter XIV - Thermodynamics of Micelles

Abstract

This chapter discusses thermodynamics of micelles. Micelles are the aggregates formed upon an increase in amphiphile concentration in water beyond some critical concentration commonly known as critical micelle concentration (CMC). The hydrophobic groups are essentially inside the roughly spherical micelle where they are shielded from the water molecules. In particular, the amphiphile is defined as a molecule which contains a solvophobic group on one side and a solvophilic group on the opposite side of the molecule. The product formed at concentration in excess of the CMC differs in a significant way from that formed in a metastable solution having non-amphiphilic solute in the transition to the equilibrium state. The latter occurs either by classical nucleation and growth, or by spinodal decomposition or by some combination of both processes. For micelles to be phases the saturated solution containing monomers and micelles at coexistence must be in equilibrium with an infinite aggregate and it is observed that the latter corresponds thermodynamically to a phase. All micelles at their smallest size are commonly spherical in shape. The chapter also highlights the characteristics of micelles.