Release of surfactants from organo-modified montmorillonite into solvents: Implications for polymer nanocomposites

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed to measure the surfactant released from organo-modified montmorillonite (OMMt) into different solvents used as food simulants. Two types of OMMt (Nanomer I.44P and Cloisite 93A) containing different quaternary alkylammonium surfactants were selected. The release of surfactant from clay suspensions was investigated by taking three factors into consideration: temperature, sonication and simulant type. At room temperature (22 °C), the amount of surfactant (in percentage) released from the OMMt into pure ethanol was about 25% (from the I44P clay) and 11% (from the Cloisite clay). However, more surfactant was released into ethanol when the clay suspensions were held at higher temperatures, and a two-fold amount of surfactant was released when the suspensions were sonicated. The maximum surfactant release from both types of OMMt was achieved when the clays were dispersed in pure ethanol, while significantly less surfactant was released into 50% ethanol (ethanol/water, 1:1) or pure water. Finally, the affinity between the solvent and the surfactant was discussed based on solubility parameters and correlated with the surfactant release into different solvents.