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Crystallization on heating and complex phase behavior of alpha-cyclodextrin solutions
M Plazanet1, M Dean, M Merlini
1LENS, University of Florence, Via Nello Carrara 1, I-50019-Sesto-Fiorentino, Italy.
Heating alpha-cyclodextrin (alpha-CD) and 4-methylpyridine (4MP) solutions causes reversible liquid-solid transitions. Five crystalline phases were identified, revealing insights into the crystallization process and disorder-order transitions.
Area of Science:
- Materials Science
- Physical Chemistry
- Crystallography
Background:
- Alpha-cyclodextrin (alpha-CD) and methylpyridines form inclusion complexes.
- These systems can exhibit complex phase behaviors upon thermal treatment.
Purpose of the Study:
- To investigate the reversible liquid-solid transitions in alpha-cyclodextrin/4-methylpyridine (alpha-CD/4MP) solutions.
- To characterize the crystalline phases and phase transformations at elevated temperatures.
Main Methods:
- Solubility measurements
- Differential scanning calorimetry (DSC)
- Quasielastic neutron scattering (QENS)
- X-ray powder diffraction (XRPD)
Main Results:
- Reversible liquid-solid transitions were observed upon heating alpha-CD/4MP solutions.
- Five distinct crystalline phases were identified for the alpha-CD/4MP system.
- Unit cell parameters indicated temperature-dependent changes, suggesting a crystallization pathway.
- A model was proposed to explain the observed disorder-order transition.
Conclusions:
- The alpha-CD/4MP system exhibits complex thermal phase behavior.
- Multiple crystalline phases form and transform with temperature.
- The findings provide a framework for understanding disorder-order transitions in such systems.
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