H-1-NMR INVESTIGATION OF THE COMPLEXATION BETWEEN BETA-CYCLODEXTRIN AND POLY(ETHYLENE OXIDE)-POLY(PROPYLENE OXIDE) BLOCK-COPOLYMERS

Complex formation of beta-cyclodextrin or its methylated derivative wi th 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 H-1 NMR spectroscopy. In the presence of cyc lodextrin, the signals due to methyl and methylene protons of the bloc k copolymers shifted to stronger fields, suggesting the formation of i nclusion complexes. Increasing the temperature shifted the signals and also affected the line shape of the signal due to methyl protons, tra nsforming the doublet to a broad singlet. Comparison of the binding cu rves plotted as the chemical shift versus molar ratio between the poly mer and cyclodextrin or its derivative reveals that the hydroxy groups of cyclodextrin are involved in the interaction with the block copoly mers.