THERMODYNAMICS OF MICELLE FORMATION BY 1-METHYL-4-ALKYLPYRIDINIUM HALIDES

This paper reports enthalpies of micellization for a series of 1-methy l-4-alkylpyridinium halide surfactants at 303.2 K with different lengt hs and degrees of branching of the 4-alkyl chain and different sizes o f counterions using two microcalorimeters (LKB 2277 and Omega Microcal ). The standard enthalpy of micellization (DELTAH-degrees(m)) becomes more exothermic with increasing chain length and with increasing size of the halide counterion. No trend could be observed with respect to t he degree of branching of the alkyl chain. Critical micelle concentrat ions (cmc) were determined as a function of temperature using conducto metry. These cmc values were used to calculate the standard Gibbs ener gy of micellization (DELTAG-degrees(m)) according to the phase separat ion model. From this we calculated the standard enthalpy of micellizat ion (DELTAH-degrees(m)), which was compared with the microcalorimetric enthalpies of micellization.