THE EFFECT OF CONCENTRATION, SOLVENT, AND TEMPERATURE ON AGGREGATION OF A COMMERCIAL CALCIUM SULFONATE ADDITIVE AS STUDIED BY FTIR AND LIGHT-SCATTERING TECHNIQUES

The aggregation of a calcium sulfonate in organic solvents was studied by the Fourier Transform Infrared (FTIR) spectroscopy and dynamic lig ht scattering techniques. The symmetric stretching band of the S=O bon d was found to be sensitive to the concentration of the additive and t o the polarity of the solvent. A critical micelle concentration (CMC) may exist in the concentration range of 0.04-0.11 millimole/liter. As the solvent polarity increased, the width in half height of the symmet ric stretching band of S=O increased, and the interaction between the solvent and the polar head of calcium sulfonate increased accordingly. This interaction weakened the interaction between the polar heads the mselves, and thereby the size of the micelle decreased as found by dyn amic light scattering. When the polarity of a solvent is strong enough , e.g., in heptanoic acid or water, the micelles formed may revert bac k to normal micelles. The FTIR spectra and aggregation size of calcium sulfonate in hexadecane showed that higher temperatures decreased the width in half height of the asymmetric stretching bands and concurren tly decreased the size of the aggregation.