title: Ultrasound-driven secondary self-assembly of amphiphilic β-cyclodextrin dimers.
abstract: The controlled secondary self-assembly of amphiphilic molecules in solution is theoretically and practically significant in amphiphilic molecular applications. An amphiphilic β-cyclodextrin (β-CD) dimer, namely LA-(CD)2 , has been synthesized, wherein one lithocholic acid (LA) unit is hydrophobic and two β-CD units are hydrophilic. In an aqueous solution at room temperature, LA-(CD)2 self-assembles into spherical micelles without ultrasonication. The primary micelles dissociates and then secondarily form self-assemblies with branched structures under ultrasonication. The branched aggregates revert to primary micelles at high temperature. The ultrasound-driven secondary self-assembly is confirmed by transmission electron microscopy, dynamic light scattering, (1) H NMR spectroscopy, and Cu(2+) -responsive experiments. Furthermore, 2D NOESY NMR and UV/Vis spectroscopy results indicate that the formation of the primary micelles is driven by hydrophilic-hydrophobic interactions, whereas host-guest interactions promote the formation of the secondary assemblies. Additionally, ultrasonication is shown to be able to effectively destroy the primary hydrophilic-hydrophobic balances while enhancing the host-guest interaction between the LA and β-CD moieties at room temperature.
authors.affiliation: The Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education and Shanxi Key Laboratory of Macromolecular Science and Technology, School of Science, Northwestern Polytechnical University, Xi'an, 710072 (P.R. China), Fax: (+86) 029-88431619.
authors.forename: Hai-tao
authors.initials: HT
authors.lastname: Zhang
authors.forename: Xiao-dong
authors.initials: XD
authors.lastname: Fan
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.forename: Rong-tian
authors.initials: RT
authors.lastname: Suo
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yang
authors.forename: Yang
authors.initials: Y
authors.lastname: Bai
authors.forename: Wan-bin
authors.initials: WB
authors.lastname: Zhang
keywords: cyclodextrins; host-guest systems; hydrophilic-hydrophobic interactions; self-assembly; ultrasonic