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

Abstract

Hydrophobically associating polymers have been obtained by chemical modification 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 precursor solutions attributed to intramolecular hydrophobic associations. At higher concentrations intermolecular associations take place. In all cases, the viscosities are of limited value. Hydrophobic microdomains were evidenced by static fluorescence measurements in the presence of pyrene and critical aggregation concentrations determined. A study of fluorescence versus temperature has shown a modification of hydrophobic properties above 40°C corresponding to a coiling of the molecules, masking the hydrophobic groups. When these modified polymers are added to solutions of β-cyclodextrin epichlorhydrin polymer (βCD/EP), associations take place between the two polymers due to inclusion of adamantyl groups in cyclodextrin cavities. High viscosity enhancements are observed which are maximum for a precise composition of both polymers. This composition corresponds to the stoechiometry 1 adamantyl group for 1 CD cavity and varies with molecular weight and hydrophobe 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 β-cyclodextrin cavities.