Preparation and Characterization of Inclusion Complexes between Methylated Cyclodextrins and Poly(tetrahydrofuran)

Binding properties of poly(tetrahydrofuran) (PTHF) to methylated cyclodextrins (CDs) in aqueous solutions were studied by turbidity titration and 1H NMR measurements. PTHF, which has a low solubility in water, was dissolved in water on addition of 2,6-di-O-methyl-β-CD (DM-β-CD) and DM-α-CD. 2,3,6-tri-O-methyl-β-CD (TM-β-CD) and TM-α-CD did not solubilize PTHF. When PTHF was mixed with aqueous solutions of DM-β-CD and TM-β-CD, the inclusion complexes crystallized after several days. 1,4-Butanediol (monomer model) and PTHF (Mw = 250) did not form crystalline complexes with methylated CDs. The yields of the complexes of PTHF with methylated β-CDs increased with increasing molecular weight of PTHF and reached a maximum at about Mw = 1000. The complexes were characterized by 1H NMR, solid-state 13C NMR, powder X-ray, and FT-IR measurements.