Preparation and Properties of 2-Amino Acid Type Amphoteric Surfactants Containing Hydroxyl Group. II.

Abstract

The 2-aminocarboxylic amphoteric surfactants containing ether and substituted amino groups such as 2- {N- [2- (2-hydroxyethoxy) ethyl]} aminofatty acid (abbreviated as (I) -Cn) and 2- {N- [N'- (2-hydroxyethyl)] aminoethyl} aminofatty acid (abbreviated as (II) -Cn) were prepared by reaction of 2-bromo fatty acid methyl ester with 2- (2-aminoethoxy) -1-ethanol or 2- (2-aminoethylamino) -1-ethanol and subsequent saponification. The methyl esters employed were ones of lauric, myristic, and palmitic acids. The isoelectric points, the critical micelle concentration (cmc) values, and the dependence of the cmc and surface tension on the pH value were determined. The relationship between log cmc and alkyl chain length (N) was expressed as the following equations; log cmc=3.00-0.382 EN for (I) -Cn and log cmc=0.33-0.336·N for (II) -Cn The cmc value of (I) -C12 in alkaline solution was higher than in acidic solution and moreover was higher than that of 2- [N, N-bis (2-hydroxyethyl)] aminododecanoic acid. The surface tension of (I) -Cn, and (II) -Cn gave a cenparatively conbined value from 30 to 47 dyn/cm over a wide pH range probably owing to the presence of ether, amino or hydroxyl group.