Aggregation of Hydrophobic Substituents of Poly(acrylate)s and Their Competitive Complexation by β- and γ-Cyclodextrins and Their Linked Dimers in Aqueous Solution

Abstract

Competition between the aggregation of the octadecyl substituents of 3% randomly substituted poly(acrylate), PAAC18, and of the dodecyl substituents of the PAAC12 analogue, and their complexation by β-cyclodextrin, βCD, the linked dimers, N,N′-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, and N,N′-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, and γ-cyclodextrin, γCD, and the analogous dimers 66γCD2ur and 66γCD2su have been studied in aqueous solution. The zero-shear viscosities of 3.3 wt % aqueous solutions of PAAC18, decreases in the presence of βCD, 66βCD2ur, 66βCD2su and γCD, is little changed in the presence of 66γCD2ur, and increases in the presence of 66γCD2su. In contrast, the zero-shear viscosities of aqueous solutions of PAAC12 increase in the presence of βCD, γCD, and their dimers but they are much less than those of the corresponding PAAC18 solutions. These macroscopic variations are due to host–guest complexation of the octadecyl and dodecyl substituents by βCD, γCD, and their dimers (as shown by 2D 1H NOESY NMR spectroscopy) competing with aggregation of the octadecyl and dodecyl substituents where differences in substituent length and cyclodextrin annular size are dominant factors.