A comprehensive study on the inclusion mechanism of benzophenone into supramolecular nanoassemblies prepared using two water-soluble associative polymers

In this study, the entrapment of benzophenone (BZ) into supramolecular nanoassemblies prepared by mixing two water-soluble associative polymers (i.e. polymerized beta-CD (p beta-CD) and dextran grafted with lauryl-side chains (MD)) has been investigated by using isothermal titration microcalorimetry (ITC) and molecular modeling. ITC experiments have been performed at various temperatures (4 degrees C (277 K), 25 degrees C (298 K), and 37 degrees C (310 K)) to evaluate the interaction of BZ with p beta-CD in comparison with beta-CD. The inclusion complexation for both beta-CD/BZ and p beta-CD/BZ interactions was entropy-driven (vertical bar Delta H vertical bar\vertical bar T Delta S vertical bar) when the temperature of the experiment was low (4 degrees C) and enthalpy-driven (vertical bar Delta H vertical bar>vertical bar T Delta S vertical bar) with minor entropic contribution when the temperature was increased (25 and 37 degrees C). Using all the thermodynamic data obtained for beta-CD/BZ and beta b-CD/BZ interactions when the temperature of the experiment was varied, the Delta H = f (T Delta S) plot was perfectly linear, which reflected an enthalpy-entropy compensation process. Finally, the combination of ITC data with molecular modeling provided consistent information in regard to the location of MD side chains and BZ inside the cyclodextrin cavity, as well as concerning the stability of the nanoassemblies loaded with BZ.