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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. [ABSTRACT FROM AUTHOR]

Abstract: We report the design and synthesis of a thermally-responsive dumbbell-shaped polymer based on one β-cyclodextrin (β-CD)-terminated polyethylene glycol (PEG) segment and several poly(N-isopropylacrylamide) (PNIPAM) segments through combining click reaction with atom transfer radical polymerization. Thermally-triggered self-assembly and molecular inclusion behaviors of the polymer were investigated by UV–vis spectroscopy, dynamic light scattering (DLS), 1H NMR in D2O, fluorescence spectroscopy and transmission electron microscopy. These results indicated that the polymer presents both thermal sensitivity and molecular inclusion properties due to the existence of PNIPAM segments and β-CD units. Above the lower critical solution temperature (LCST) of PNIPAM segment, the polymer can self-assemble into nano-sized assemblies, where PNIPAM segments serve as the core and PEG segments are organized as the corona. By using 1-adamantane acid sodium as guest molecule, the polymer shows size-adjusted aggregation behaviors based on the inclusion interactions between β-CD and guest molecule. [Copyright &y& Elsevier]