(88f) The Effect of Surfactant Polydispersity In Phase Change Emulsification

An effective method for the preparation of fine (less than about 300 nm volume average particle size) emulsions is phase change emulsification.  In this process, microemulsions are converted by compositional and temperature changes to give oil in water emulsions (“nanoemulsions”) in which the high interfacial area of the microemulsion is “captured.”  Problems for practical implementation of phase change emulsification include formation of precursor microemulsions in a useful temperature range and subsequent conversion of the microemulsion to give a nanoemulsion.  Both steps are highly dependent upon polydispersity in the HLB values of the surfactants used. Surfactant HLB polydispersity results from mixtures of high and low HLB surfactants, which may occur for example, through the use of low HLB hydrophobic linkers. HLB polydispersity appears to promote lamellar character in microemulsions and gives optimal results in the case of providing moderate levels of lamellar character.