1 research outputs found
Unusually High Efficiency of β‑Cyclodextrin Clathrate Preparation by Water-Free Solid-Phase Guest Exchange
An effective preparation procedure
is offered for β-cyclodextrin
(bCD) clathrates with volatile guests of moderate hydrophilicity,
which otherwise require a finely tuned optimization of the bCD/water/guest
ratio. The proposed procedure includes guest exchange in a water-free
bCD matrix. As a result, more stable clathrates with a higher inclusion
capacity can be prepared than by direct saturation of dried or hydrated
bCD. To find an optimal preparation method, the structure–property
relationships were studied for four different ways of bCD clathrate
formation with guests of varying molecular structure. The study was
much simplified by used procedures excluding direct contact of guest
and water liquids with bCD. Besides, in clathrate preparation experiments,
the thermodynamic activities of water and guest were varied independently,
which makes explicit the role of water in this process. Hydration
of bCD reduces its inclusion threshold for hydrophobic guests by their
activity (relative vapor pressure), giving favorable hydration effect
for their inclusion. Besides, water competes with hydrophilic guests
for binding sites in bCD at high water activities. Together with bCD
dehydration by excess of hydrophilic guests, these observations give
a complete thermodynamic picture, which may be fruitful for elaboration
of guest encapsulation techniques by cyclodextrins