Aggregation Behavior and Thiol-Thioester Exchange for Cationic Surfactants with Propylthioacetate Side Chain

[Abstract] : A series of cationic surfactants containing the thioacetate group, [CnH2n+1N(CH3)2(CH2)3SCOCH3] Cl(Cn3SAc, n=12,14,16) , were prepared and their properties in aqueous solution were investigated by conductivity, fluorescence, and dynamic light scattering measurements. The critical micelle concentrations (CMCs) of Cn3SAc decreased to about half the value of the corresponding alkyltrimethylammonium chloride. Thioacetate was eliminated with the addition of dithiothreitol (DTT) as well as NaOH. HPLC (high performance liquid chromatography) analysis and NMR (nuclear magnetic resonance) spectroscopy showed that thiol surfactants, [CnH2n+1N(CH3)2(CH2)3SH]Cl(Cn3SH) , were generated upon the addition of DTT in aqueous solution via thiol-thioester exchange, whereas gemini surfactants, [CnH2n+1N(CH3)2(CH2)3SS(CH2)3N(CH3)2CnH2n+1]2Cl(2Cn3SS) , were generated upon incubation in alkaline solution via hydrolysis and air oxidation.