title: The excellent water-solubility of N-[3-(dimethyl-amino)propyl] docosanamide chloride : the most eco-friendly cationic hair conditioning agent.
abstract: A new hair-conditioning agent, N-[3-(dimethylamino)propyl]docosanamide (APA-22) hydrochloric acid salt (APA-22 HCl), has excellent solubility in water with a solubility limit over 10-times larger than that of other APA hydrochloric salts with shorter alkyl chain lengths. The physicochemical characteristics of APA-22 HCl were studied at 25 degrees C by using equilibrium surface tension (gamma), solubilization of an oil-soluble dye, steady-state fluorescence, and chloride ion selective electrode techniques. The APA-22 HCl salt is considered to form an aggregate at a concentration, C(1), which is about twice the concentration of the solubility limit of APAs with shorter alkyl chains. At a higher concentration, C(2), the aggregates of APA-22 HCl start forming another kind of aggregate, which is able to solubilize oil-soluble materials. That is, C(1) is considered to represent the critical aggregation concentration (cac) and C(2) a morphology transition. In the concentration region between C(1) and C(2) the solutions are seemingly transparent whereas at above C(2) they appear bluish or translucent. Since the Krafft point of APA-22 HCl is 55 degrees C, all the solutions, including the aggregates, are thought to exist in metastable states. Notably, however, these metastable solutions do not change significantly over a few months. The excellent solubility of APA-22 HCl in water is considered to be a result of this unique stepwise aggregation with increasing concentration.
authors.affiliation: Material Science Research Laboratories, KAO Corporation, Wakayama, Japan. sakai.takaya@kao.co.jp
authors.forename: Takaya
authors.initials: T
authors.lastname: Sakai
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Inoue
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamane
authors.forename: Takamasa
authors.initials: T
authors.lastname: Toyo
authors.forename: Naohiro
authors.initials: N
authors.lastname: Nishiyama
authors.forename: Youhei
authors.initials: Y
authors.lastname: Kaneko
mesh_terms: D000577:Amides / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D002712:Chlorides / Q000032:analysis; D004396:Coloring Agents / Q000737:chemistry; D017753:Ecosystem; D006203:Hair Preparations / Q000737:chemistry*; D008823:Micelles; D015394:Molecular Structure; D012995:Solubility; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D000577:Amides; D002412:Cations; D002712:Chlorides; D004396:Coloring Agents; D006203:Hair Preparations; D008823:Micelles; D013501:Surface-Active Agents; D014867:Water; C533672:N-(3-(dimethylamino)propyl)docosanamide