title: Structure and growth behavior of centimeter-sized helical oleate assemblies formed with assistance of medium-length carboxylic acids.
abstract: The nonequilibrium organization of self-assemblies from small building-block molecules offers an attractive and essential means to develop advanced functional materials and to understand the intrinsic nature of life systems. Fatty acids are well-known amphiphiles that form self-assemblies of several shapes. Here, we found that the lengths of helical structures of oleic acid formed in a buffered aqueous solution are dramatically different by the presence or absence of certain amphiphilic carboxylic acids. For example, under the coexistence of a small amount of N-decanoyl-l-alanine, we observed the formation of over 1 centimeter-long helical assemblies of oleate with a regular pitch and radius, whereas mainly less than 100 μm-long helices formed without this additive. Such long helical assemblies are unique in terms of their highly dimensional helical structure and growth dynamics. Results from the real-time observation of self-assembly formation, site-selective small-angle X-ray scattering, high-performance liquid chromatography analysis, and pH titration experiments suggested that the coexisting carboxylates assist in elongation by supplying oleate molecules to a scaffold for oleate helical assembly.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan. y.kageyama@mail.sci.hokudai.ac.jp stakeda@sci.hokudai.ac.jp.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kageyama
authors.forename: Tomonori
authors.initials: T
authors.lastname: Ikegami
authors.forename: Natsuko
authors.initials: N
authors.lastname: Hiramatsu
authors.forename: Sadamu
authors.initials: S
authors.lastname: Takeda
authors.forename: Tadashi
authors.initials: T
authors.lastname: Sugawara