Ultrasound-Driven Secondary Self-Assembly of Amphiphilic β-Cyclodextrin Dimers

• Published in: Chemistry : a European journal Vol. 21; no. 13; pp. 5000 - 5008
• Main Authors: Zhang, Hai-tao, Fan, Xiao-dong, Tian, Wei, Suo, Rong-tian, Yang, Zhen, Bai, Yang, Zhang, Wan-bin
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23.03.2015; WILEY‐VCH Verlag; Wiley
• Subjects: Aggregates; Aqueous solutions; Branched; Chemistry; Chemistry, Multidisciplinary; cyclodextrins; Dimers; Formations; host-guest systems; hydrophilic-hydrophobic interactions; Micelles; Physical Sciences; Science & Technology; Self assembly; Spectroscopy; ultrasonic; TOBACCO-MOSAIC-VIRUS; AQUEOUS-SOLUTIONS; host-guest systems; ACID; RESOLUTION; MICELLES; cyclodextrins; ultrasonic; hydrophilic-hydrophobic interactions; TRANSITION; self-assembly; THERMODYNAMICS; MOLECULAR RECOGNITION; BOND; COMPLEXATION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201405707

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, 1H NMR spectroscopy, and Cu2+‐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. One from the other: An amphiphilic β‐cyclodextrin (β‐CD) dimer, consisting of one hydrophobic lithocholic acid (LA) unit and two β‐CD units, was synthesized and its self‐assembly into spherical micelles in aqueous solution without ultrasonication was observed. Initially, the primary micelles dissociated under the action of ultrasonication; then, secondary self‐assemblies possessing a branched morphology were formed by further increasing the ultrasonication time.