Complex formation of poly(epsilon-caprolactone) with cyclodextrins

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