Micellization and adsorption of a series of succinimide dispersants

The efficiency of a series of nonionic dispersants at stabilizing carbon-rich particles in oil was evaluated. The dispersants were synthesized by coupling a polyamine to two polyisobutylenes terminated at one end with a succinic anhydride (PIBSA). Their chemical composition was characterized by FTIR absorption. The associative strength of the dispersants was determined from their ability to self-associate in solution into reverse micelles. Their critical micelle concentration (CMC) and aggregation number (Nagg) were determined by fluorescence in an apolar solvent, namely hexane. The associative strength of the dispersants was found to increase with increasing number of secondary amines in the polyamine core. The adsorption isotherms describing the adsorption of the dispersants onto carbon black particles were determined and showed the existence of two binding regimes for the dispersants having more amines in their polar core. Much stronger binding occurred at dispersant concentration lower than the CMC. The weaker binding observed at dispersant concentrations larger than the CMC is believed to result from the dispersants having to compete between micellization and adsorption at concentrations above the CMC.