Self-assembly of nonionic surfactant Tween 20@2β-CD inclusion complexes in dilute solution

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Traditionally, cyclodextrins (CDs) were thought to inhibit surfactant self-assembly in dilute solutions by disrupting hydrophobic interactions.
• The formation of hydrophilic cyclodextrin/surfactant inclusion complexes was believed to prevent self-assembly.
• This prevailing view limited the exploration of CDs in surfactant self-assembly systems.

Purpose of the Study:

• To investigate the self-assembly behavior of β-cyclodextrin (β-CD) and nonionic surfactant inclusion complexes in dilute solutions.
• To identify the building blocks and driving forces behind the observed self-assembly.
• To explore the potential of these complexes as novel components for nonamphiphilic self-assembly.

Main Methods:

• Utilized Nuclear Magnetic Resonance (NMR) spectroscopy (specifically HNMR) to characterize the inclusion complex.
• Employed Mass Spectrometry (MS) to confirm the composition of the self-assembled structures.
• Conducted Infrared (IR) spectroscopy and structural analysis to elucidate the intermolecular interactions.

Main Results:

• β-CD/nonionic surfactant inclusion complexes self-assembled into vesicles even at concentrations below the critical micelle concentration (CMC) of the surfactants.
• For Tween 20 and β-CD, the fundamental building block was identified as the Tween 20@2β-CD inclusion complex.
• Hydrogen bonding between the Tween 20 headgroup and β-CD hydroxyl groups was identified as the primary driving force for self-assembly.

Conclusions:

• The self-assembly of β-CD/nonionic surfactant inclusion complexes into vesicles in dilute solutions is a general phenomenon.
• Surfactant@2β-CD inclusion complexes represent a novel class of building blocks for nonamphiphilic self-assembly.
• This finding offers new insights into the influence of cyclodextrins on surfactant self-assembly mechanisms.