THERMODYNAMICS OF MICELLIZATION OF SOME NEW PYRIMIDINIUM CATIONIC SURFACTANTS

The thermodynamics of micellization of some new pyrimidinium cationic surfactants were studied at four different temperatures by determining the critical micelle concentration. These new surfactants contain a positively charged nitrogen atom of the pyrimidine ring with a long chain alkyl group of 12-18 carbons. The thermodynamic quantities so determined show odd-even behaviour. At any one temperature the free energy of micellization shows an increasing negative value with increase in the carbon number of the alkyl group for even members of the homologous series. The same is also the case with the odd members of the homologous series. The micellization is endothermic and the entropy changes are all positive, showing that the systems become less structured.