ABSTRACT
Novel trimeric surfactants consisting of three units of sodium N-acyl-L-cysteine linked with hexahydro-1,3,5-triazine as the central core ((CnCy)3Na3, where n represented alkyl chain carbon number of 8, 10, and 12) were synthesized. Their conjugated acids were analyzed using FTIR, NMR, and ESI-MS to elucidate their chemical structures. The surface activity properties of (CnCy)3Na3 were determined using surface tension and electrical conductivity measurements. It was found that (C12Cy)3Na3 had a critical aggregation concentration (CAC) two orders of magnitude lower than that of the corresponding monomeric surfactant sodium N-lauroyl-L-cysteine (C12CyNa). The value of the minimum surface area per molecule (Amin) of (C12Cy)3Na3 was almost three times greater than that of C12CyNa due to the increase in the degree of oligomerization. With the alkyl chain length increasing from 8 to 12, the CAC values decreased, and the values of the surface tension at CAC (γCAC) and the efficiency of the surface adsorption (pC20) increased. Furthermore, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to evaluate the size and morphology of the aggregates at 10CAC. The results indicate that (CnCy)3Na3 can spontaneously self-assemble into spherical or ellipsoid aggregates, and the surfactants with longer chain length can form larger aggregates due to greater hydrophobic interactions.
GRAPHICAL ABSTRACT
![](/cms/asset/1c9cd2dd-cac7-4ab4-83e1-8b432c11729a/ldis_a_1307762_uf0001_b.png)