1H NMR investigation of the complexation between β-cyclodextrin and poly(ethylene oxide)-poly(propylene oxide) block copolymers

Complex formation of B-cyclodextrin or its methylated derivative with poly(ethylene oxide)-poly(propylene oxide) block copolymers of EPE and PEP types (E is for ethylene oxide, P is for propylene oxide) was studied in solution using 1H NMR spectroscopy. In the presence of cyclodextrin, the signals due to methyl and methylene protons of the block copolymers shifted to stronger fields, suggesting the formation of inclusion complexes. Increasing the temperature shifted the signals and also affected the line shape of the signal due to methyl protons, transforming the doublet to a broad singlet. Comparison of the binding curves plotted as the chemical shift versus molar ratio between the polymer and cyclodextrin or its derivative reveals that the hydroxy groups of cyclodextrin are involved in the interaction with the block copolymers.