title: Structure and stability of columnar cyclomaltooctaose (gamma-cyclodextrin) hydrate.
abstract: Rapid recrystallization of cyclomaltooctaose (gamma-cyclodextrin, gamma-CD) from aqueous solution resulted in formation of a columnar structure with only water as the guest molecule. Upon vacuum drying at 90 degrees C for 15 h, gamma-CD, which was initially in the columnar structure, became amorphous. Complementary water vapor sorption and wide-angle X-ray diffractometry experiments were performed on columnar gamma-CD in its vacuum dried and as-precipitated states to elucidate its stability in humid environments and the crystal structure present at varying sorption levels. These experiments show that both types of gamma-CD transform to the cage crystal structure upon exposure to water vapor at 40 degrees C and with an activity of 1.0. Sorption equilibrium is reached long before the crystal structure transformation is complete, indicating that a significant amount of molecular mobility exists in the various hydrated gamma-CD crystal structures.
authors.affiliation: Fiber and Polymer Science Program, Campus Box 8301, North Carolina State University, Raleigh, NC 27695-8301, USA.
authors.forename: Marcus A
authors.initials: MA
authors.lastname: Hunt
authors.forename: Cristian C
authors.initials: CC
authors.lastname: Rusa
authors.forename: Alan E
authors.initials: AE
authors.lastname: Tonelli
authors.forename: C
authors.initials: C
authors.lastname: Maurice Balik
mesh_terms: D003460:Crystallization; D015394:Molecular Structure; D012996:Solutions / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction; D047408:gamma-Cyclodextrins / Q000737:chemistry*
chemical_list: D012996:Solutions; D047408:gamma-Cyclodextrins; D014867:Water; C023792:gamma-cyclodextrin