Surfactants in Disperse Systems

Surface active agents (usually referred to as surfactants) are amphipathic molecules that consist of a non-polar hydrophobic portion, usually a straight or branched hydrocarbon or fluorocarbon chain containing 8-18 carbon atoms, which is attached to a polar or ionic portion (hydrophilic) (see Chapter 1). The hydrophilic portion can be nonionic, ionic or zwitterionic, accompanied by counter ions in the last two cases. 

The hydrocarbon chain interacts weakly with water molecules, whereas the polar or ionic head group interacts strongly with water molecules (ion-dipole or dipole-dipole interaction). The strong interaction of the head group with water molecules renders the surfactant molecule soluble in water. Cooperative action of dispersion and hydrogen bonding between the water molecules tends to squeeze the hydro-phobic group out of the water (hydrophobic chains). 

The balance between hydrophilic and hydrophobic part of the chain (sometimes referred to as the hydrophilic lipophilic balance, HLB) gives these molecules their special properties Accumulation at various interfaces (adsorption) association in solution to form micelles. 

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