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Published on: June 20, 2019
Solid crystal network of self-assembled cyclodextrin and nonionic surfactant pseudorotaxanes
Andrés Guerrero-Martínez1, David Avila, Francisco J Martínez-Casado
1Physikalisches Institut, Wesfälische Wilhelms Universität Münster, Germany. aguerrero@uvigo.es
The Journal of Physical Chemistry. B
|August 14, 2010
Summary
Nonionic surfactants and beta-cyclodextrin form ordered supramolecular crystals. This study demonstrates their use in creating self-assembled pseudorotaxane crystals, offering alternatives to traditional polymer threading methods.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Crystal Engineering
Background:
- Cyclodextrins (CDs) are widely used in supramolecular chemistry to form inclusion complexes.
- Polyrotaxanes are supramolecular structures typically formed by threading cyclic molecules onto linear polymer chains.
- Nonionic surfactants offer potential as alternative threading components for supramolecular assemblies.
Purpose of the Study:
- To investigate the self-assembly of pseudorotaxanes formed by nonionic surfactants and beta-cyclodextrin (beta-CD).
- To characterize the resulting three-dimensional crystal structures.
- To explore the potential of nonionic surfactants as linear threads for synthesizing supramolecular crystals.
Main Methods:
- X-ray powder diffraction (XRPD) for crystal structure analysis.
- High-resolution transmission electron microscopy (HRTEM) for morphological characterization.
- Solid-state (13)C cross-polarization magic-angle spinning (CP/MAS) Nuclear Magnetic Resonance (NMR) spectroscopy.
- Single crystal X-ray diffraction for detailed structural determination.
Main Results:
- Formation of three-dimensional crystals of self-assembled pseudorotaxanes in aqueous solution.
- Lamellar self-assembly with preferential orientation and disorder observed in the crystal structure.
- Single crystal analysis revealed a triclinic unit cell (P1) containing beta-CD dimers threaded by the surfactant.
- The pseudorotaxane structure involves beta-CD dimers complexing both hydrophilic and hydrophobic parts of the surfactant.
Conclusions:
- Nonionic surfactants, specifically Igepal CO-520, can effectively act as linear threads for beta-cyclodextrin.
- Ordered self-assembly into supramolecular polyrotaxane solid crystals is achieved through hydrogen-bonded beta-CD dimers.
- Nonionic surfactants provide a viable alternative to polymers for synthesizing supramolecular polyrotaxane crystals with CDs.
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