INTERFACIAL CHARACTERIZATION OF SUCCINIMIDE SURFACTANTS

The interfacial and nonaqueous solution properties of model engine oil antisludge dispersants have been characterized. Straight chain C-8-C- 18 mono, bis, and tris succinimides were synthesized with polar headgr oups of different dimensions and varying nitrogen content. These molec ules were found to be poorly soluble in water, as confirmed by log P c alculations (P is the partition function between octan-1-ol and water. ) Vapor pressure osmometry measurements carried out in acetone and tol uene revealed that the mono succinimides show evidence of association into clusters of about three molecules with no noticeable chain length dependence, whereas the bis and tris compounds are essentially unasso ciated in these solvents. Surface pressure vs area curves from a Langm uir trough exhibit a characteristic plateau at low surface coverage, e specially for short chain lengths and mono-substituted succinimides. T his feature we attribute to a more compact packing of the headgroups u nder pressure. For the same lateral pressure the area occupied increas es in the order: mono, bis, and tris, correlating well with the number of succinimide moieties in the headgroup. Ellipsometry performed on t hese molecules deposited on silicon wafers showed that the molecules g enerally formed excellent close-packed Langmuir-Blodgett films. The su ccinimides are extremely effective at binding to polar substrates, whi ch is consistent with their practical use. For example, solutions of t he various compounds deposited on TLC plates generally showed little m ovement, and there was the maximum amount of separation in those cases where the solvent had a natural affinity for the headgroup or tail.