Formation of host-guest complexes of β-cyclodextrin and perfluorooctanoic acid.

Structural characterization and dynamic properties of solid-state inclusion complexes of β-cyclodextrin (β-CD) with perfluorooctanoic acid (PFOA) were investigated by 19F/13C solid-state and 19F/1H solution NMR spectroscopy. The complexes in the solid state were prepared using dissolution and slow cool methods, where thermal analyses (DSC and TGA), PXRD, and FT-IR results provided complementary support that inclusion complexes were formed between β-CD and PFOA with variable stoichiometry and inclusion geometry. 19F DP (direct polarization) and 13C CP (cross-polarization) with magic-angle spinning (MAS) solids NMR, along with 19F/1H solution NMR were used to characterize the complexes in the solid and solution phases, respectively. The dynamics of the guest molecules in the inclusion complexes (ICs) were studied using variable temperature (VT) 19F DP/MAS NMR experiments in the solid state. The guest molecules were observed to be in several different molecular environments, providing strong evidence of vari...