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 propylene 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. Pluronic forms a monolayer, stable at the surface pressure 5 mN/m, which reacts with heptakis-(2,6-di-O-methyl)-beta-cyclodextrin and does not react with alpha- and beta-cyclodextrins. The absence of the reaction in the case of alpha-cyclodextrin is explained by the fact that the polymer 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 pluronic monolayer. After introducing heptakis-(2,6-di-O-methyl)-beta-cyclodextrin into the aqueous subphase under the pluronic monolayer an instant increase in the area is observed. An increase in the amount of heptakis-(2,6-di-O-methyl)-beta-cyclodextrin in the aqueous phase causes first steep linear increase in the monolayer area, then its leveling off at the polymer heptakis-(2,6-di-O-methyl)-beta-cyclodextrin ratio equal to about 1:15. This value correlates well with a stoichiometric composition of the similar complex in solution.