Reversible Transition between SDS@2β-CD Microtubes and Vesicles Triggered by Temperature

Abstract

Switching between association and dissociation is the well-known strategy for constructing responsive materials based on the host-guest complexes of cyclodextrins (CDs). In this work, we report that temperature may also trigger self-assembly transition in the supramolecular system composed of sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD) at a molar ratio of 1:2. We reported previously that, at this ratio, SDS and β-CD form a channel-type SDS@2β-CD supramolecular unit, which further self-assembles into non-amphiphilic vesicles and microtubes driven by hydrogen bonding. Here, we report that the vesicles and microtubes can be reversibly switched between each other upon decreasing and increasing temperature. Control experiments in heavy water suggest that water molecules play a dominating role in the hydrogen bonding between SDS@2β-CD supramolecular units at lower concentration and higher temperature. Under opposite conditions, the hydrogen bonding between CDs is dominating. Therefore, for the 5% system, we observed a vesicle to microtube transition with a decreasing temperature, whereas for the 10% system, we observed the reverse process. Both processes are reversible. This is not only an example of temperature-triggered responsiveness in non-amphiphilic self-assemblies but also a new mode of responsiveness for the host-guest inclusion systems based on CDs. This temperature-responsive process is anticipated to shed light on the design and development of novel advanced materials.

Spontaneous Self‐Assembly of γ‐Cyclodextrins in Dilute Solutions with Tunable Sizes and Thermodynamic Stability

“…Recently, hydrogen bonding was reported as the driving force for the formation of bilayer vesicles in the dilute solution of CD‐surfactant inclusion complexes,6a, b which implies the possible existence of H‐bonds in our system. The morphology of the self‐assembly of CD‐surfactant inclusion complexes is concentration‐ and temperature‐dependent, demonstrating a transition from vesicles to microtubes at a lower temperature and a higher concentration.…”

“…The functionalized ionic domains of CDs such as phosphate groups in γ‐CD‐P are also capable of forming strong H‐bonds. Previous studies indicated that the H‐bonds of CDs in aqueous solution are critical to determine the size of their assemblies 6b. Although we do not consider hydrogen bonding as the main driving force for γ‐CD‐P self‐assembly, we expect both counterion‐mediated attraction and H‐bonds will contribute to the attractive force and influence the size of blackberry structures.…”

Advanced Molecular Self-Assemblies Facilitated by Simple Molecules

“…At temperature above 42°C, the hydrogen bonding in this system is greatly retarded so that the tubes tend to transform into vesicle and the vesicles tend to break. 62 Electrostatic interactions were found to determine the critical self-aggregation concentration of the system. The presence of ionic repulsion requires a higher concentration to form selfassembled structures, whereas in nonionic surfactant systems this aggregation concentration is greatly lowered.…”

Unusual pH-regulated surface adsorption and aggregation behavior of a series of asymmetric gemini amino-acid surfactants

“…Among these aberrant properties, one noteworthy phenomenon is that the cmc of some gemini surfactants increases when the chain length of the alkyl hydrophobic group goes beyond a critical length. 24,25 Either the surfactant structure or the mixing ratio has a great inuence on the morphology of the generated aggregates. 16 Self-assemblies of surfactants such as micelles and vesicles have attracted much attention for their potential applications.…”