Complex Formation of Poly(ε-caprolactone) with Cyclodextrins

Cyclodextrins (CDs) have been found to form inclusion complexes with poly(∈-caprolactone) (PEC) to give crystalline compounds. α- and γ-CD formed complexes with these polyesters in high yields, although β-CD gave complexes in moderate yields. The yields of the complexes decreased with increasing molecular weight of the polymer. α-CD-PEC complexes are stoichiometric one-to-one (cyclodextrin: monomer unit) compounds, and γ-CD-PEC complexes are one-to-two compounds when the molecular weights of PEC are low. The complexes were isolated and characterized by 1 H NMR, 13 C CP/MAS NMR, and X-ray diffraction studies. The inclusion modes are discussed.