Association of hydrophobically modified poly (N,N-dimethylacrylamide hydroxyethylmethacrylate) with water soluble beta-cyclodextrin polymers

Hydrophobically associating polymers have been obtained by chemical modific ation of poly (N,N-dimethyl acrylamide hydroxyethylmethacrylate) consisting in the introduction of adamantyl groups (Ad). Viscosity studies of dilute solutions of modified polymers show lower reduced viscosities than precurso r solutions attributed to intramolecular hydrophobic associations. At highe r concentrations intermolecular associations take place. In all cases, the viscosities are of limited value. Hydrophobic microdomains were evidenced b y static fluorescence measurements in the presence of pyrene and critical a ggregation concentrations determined. A study of fluorescence versus temper ature has shown a modification of hydrophobic properties above 40 degrees C corresponding to a coiling of the molecules, masking the hydrophobic group s. When these modified polymers are added to solutions of beta-cyclodextrin epichlorhydrin polymer (beta CD/EP), associations take place between the t wo polymers due to inclusion of adamantyl groups in cyclodextrin cavities. High viscosity enhancements are observed which are maximum for a precise co mposition of both polymers. This composition corresponds to the stoechiomet ry 1 adamantyl group for 1 CD cavity and varies with molecular weight and h ydrophobe content of the modified polymer. Associative phase diagrams were stated which confirm the strong association of both polymers via inclusion of adamantyl groups in the beta-cyclodextrin cavities. (C) 1999 Elsevier Sc ience B.V. All rights reserved.