Synthesis and Surface-Active Properties of Trimeric-Type Anionic Surfactants Derived from Tris(2-aminoethyl)amine

摘要

Trimeric-type anionic surfactants (3C_n taAm,where n is a hydrocarbon chain length of 8,10,or 12) with three hydrocarbon chains and three carboxylate headgroups were synthesized from tris(2-aminoethyl)amine,and their properties were investigated by surface tension,electrical conductivity,dynami and static light-scattering,fluorescence of pyrene,and emulsification power techniques.The critical micelle concentrations (CMC) of 3C_ntaAm were 0.00092-0.00834 mmol dm~(-3),and the surface tensions at the CMC were 33.3-39.9 mN m~(-1).The areas per molecule occupied by 3C_10taAm and 3C_12taAm were extremely small,showing they were highly compact at the air/water interface.In addition,adsorption or micellization behavior of 3C_ntaAm waas estimated by parameters such as pC_20 (the efficiency of surface adsorption),CMC/C_20 (the ease of adsorption relative to the ease of micellization),and DELTAG_M~o (Gibbs energy of micellization).Dynamic and static light-scattering measurements of 3C_ntaAm showed a hydrodynamic radius of 45-621 nm above the CMC and aggregation numbers of 10-82 at the CMC,respectively.The fluorescence intensity ratio of the first to the third band in the emission spectra of pyrene started to lower from far above the CMC for 3C_8taAm and 3C_10taAm,and below the CMC for 3C_12taAm.This suggests that loose micelles or premicellar aggregates are formed in solutions.Mixture of aqueous solutions of 3C_ntaAm and toluene formed oil-in-water-type emulsions,and the stabilizing abilities were in the order of 3C_8taAm>3C_10taAm.The degee of emulsification of 3C_8taAm remained at 69% after 24h of standing.Thus,3C_ntaAm exhbited unique properties superior to monomeric or dimeric surfactants that were significantly inflenced by their hydrocarbon chain lengths.