S. Tanada et al., ADSORPTION BEHAVIOR OF WATER-MOLECULES ONTO ALPHA-CYCLODEXTRIN, BETA-CYCLODEXTRIN, AND GAMMA-CYCLODEXTRIN AND BRANCHED ALPHA-CYCLODEXTRINS, Journal of colloid and interface science, 181(1), 1996, pp. 326-330
Moisture adsorption properties of alpha-, beta-, and gamma-cyclodextri
n (CD) and branched alpha-CDs were investigated to elucidate the basis
of the results of adsorption isotherms of water at 10, 20, and 30 deg
rees C, the differential heat of adsorption, the entropy of the adsorb
ed water, and the heat of immersion in water, It is concluded that the
water molecules were adsorbed on the hydroxyl groups of the glucose m
olecule of alpha-CD, were first adsorbed on that of beta-CD and then w
ere included in the pore structure of beta-CD, and were only included
in the pare structure of gamma-CD. Branched alpha-CDs were developed a
nd produced to increase the interaction with water molecules. However,
the interaction between the branched alpha-CDs and the water was smal
ler than that between the virgin alpha-CD and the water, The solubilit
y of branched, alpha-CD required a long time because the heat of immer
sion was larger in the order G(2)-alpha-CD and G(1)-alpha-CD or alpha-
CD, It is considered that the side chain, glucosyl and maltosyl groups
, decreased the interaction between the water molecule and the surface
of the CD because of steric hindrance. Therefore, it is concluded tha
t the side chain inhibited the melter adsorption of the inner molecule
of CD. (C) 1996 Academic Press, Inc.