Abstract
Complexane-type trimeric surfactants of tris(1-carboxyalkyl-2-aminoethyl)amine (3Rntata; n means alkyl chain length, n=6-14) having three alkyl chains and three hydrophilic groups were prepared by the reaction of tris(2-aminoethyl)amine and 2-bromoalkanoic acid and examined for surface activities such as surface tension, emulsification and interfacial tension. Critical micelle concentration (cmc) of 3Rntata shifted to lower concentration with increasing alkyl chain length. The cmcs of 3Rntata with n of 10-14 were lower by about 1-2 orders of magnitude than those of complexane-type monomeric surfactant of 2-aminoalkanoic acid (RnNAc) and dimeric surfactant of N, N″-bis(1-carboxyalkyl)diethylenetriamine (2Rndtda) with the same alkyl groups. In the case of R12, 3Rntata gave about twice cmc of trimeric surfactant of (N1-carboxyalkyl-2-aminoethyl)alkyllamine (3Rntata) having three alkyl chains and two hydrophilic groups. Surface tension at each cmcs of 3R10tata, 3R12tata, and 3R14tata was 33.0, 26.9 and 29.6 mN m-1, respectively. 3R12tata, and 3R14tata gave more efficient in lowering the sufface tension than RnNAc and 2Rndtda. The values of cross-sectional molecular area (A) of 3Rntata with n of 10-14 were 42-75Å2. They were extremely small in comparison with three times of A of RnNAc. The aqueous solutions of 3Rntata were emulsified by shaking with toluene. Highly stable oil-in-water type emulsion was formed by using 3Rntata with n of 10-14 and the degree of emulsification was kept 60% after 20 h. Interface between the aqueous solutions of 3R10tata, 3R12tata, 3R14tata and toluene gave the interfacial tension of 1, 1 and 6 mN m-1, respectively.
