P. Umbach et al., LIGHT-SCATTERING-STUDIES ON THE CRYSTALLIZATION TRANSITION OF NATIVE AND PER-2,6-DIMETHYLATED BETA-CYCLODEXTRINS, Journal of the American Chemical Society, 118(39), 1996, pp. 9314-9319
The initial crystallization phase of native and dimethylated beta-cycl
odextrins (beta-CD) was investigated with small-angle static light sca
ttering. Following simple considerations, one can obtain the crystalli
zation exponent, predicted by the Avrami theory, from temperature quen
ching experiments. We found that a single-step mechanism, in accordanc
e with the classical theory, holds for the crystal formation of native
beta-cyclodextrin. The crystal formation mechanism of the heptakis (2
,6)-di-O-methyl)-beta-CD is more complex, and involves a fast and a sl
ow process. The exponents determined for each process indicate that cr
ystallization starts with the formation of spherical clusters which ag
gregate further to form rod-shaped macrocrystals, in accordance with m
icroscopic observations. In either case the determined exponents depen
d on the initial cyclodextrin concentration.