Complexation of dodecyl-substituted poly(acrylate) by linked β-cyclodextrin dimers and trimers in aqueous solution

Two-dimensional NOESY ¹H NMR, isothermal titration calorimetric (ITC), and rheological studies of host-guest complexation by β-cyclodextrin, β-CD, and the β-CD groups of the linked β-CD dimers, β-CD₂ur and β-CD₂su and trimers, β-CD₃bz and β-CDen₃bz, of the dodecyl, C12, substituents of the 3.0% substituted poly(acrylate), PAAC12, in aqueous solution are reported. Complexations by β-CD, β-CD₂ur, β-CD₂su, β-CD₃bz, and β-CDen₃bz of the C12 substituents of PAAC12 in 0.2 wt % solution exhibit complexation constants 10^-4K₁₁ (298.2 K)0.83, 5.80, 4.40, 15.0, and 1.50 dm³ mol^-1, respectively. (The corresponding ΔH₁₁ and TΔS₁₁ show a linear relationship.) The rheologically determined zero-shear viscosities of 3.3 wt % aqueous solutions of PAAC12 alone and in the presence of β-CD, β-CD₂ur, β-CD₂su, β-CD₃bz, and β-CDen₃bz (where the β-CD groups and C12 substituents are equimolar) are 0.016, 0.03, 0.12, 0.25, 0.12, and 0.08 Pa s (298.2 K), respectively, and show PAAC12 to form interstrand cross-links through complexation.