MONOMOLECULAR FILMS OF PLURONIC CYCLODEXTRIN INCLUSION COMPLEXES AT THE WATER-GAS INTERFACE

This paper reports the synthesis and characteristics of inclusion type complexes between amphiphilic block copolymer of ethylene and propyle ne oxides (pluronic) and alpha-, beta-, and heptakis-(2,6-di-O-methyl) -beta-cyclodextrins. The process was investigated in monolayers at the water-gas interface according to Langmuir-Blodgett technique. Pluroni c forms a monolayer, stable at the surface pressure 5 mN/m, which reac ts with heptakis-(2,6-di-O-methyl)-beta-cyclodextrin and does not reac t with alpha- and beta-cyclodextrins. The absence of the reaction in t he case of alpha-cyclodextrin is explained by the fact that the polyme r guest does not fit into a small cavity of the macrocyclic host, but for beta-cyclodextrin it may be explained by its low surface activity and, hence, its low local concentration in the vicinity of the pluroni c monolayer. After introducing heptakis-(2,6-di-O-methyl)-beta-cyclode xtrin into the aqueous subphase under the pluronic monolayer an instan t increase in the area is observed. An increase in the amount of hepta kis-(2,6-di-O-methyl)-beta-cyclodextrin in the aqueous phase causes fi rst steep linear increase in the monolayer area, then its leveling off at the polymer heptakis-(2,6-di-O-methyl)-beta-cyclodextrin ratio equ al to about 1:15. This value correlates well with a stoichiometric com position of the similar complex in solution.