Poly(vinyl alcohol) Functionalized β-Cyclodextrin as an Inclusion Complex

Abstract

Hydrophilic poly(vinyl alcohol) functionalized β -cyclodextrin polymers were synthesized by copolymerization through a mixture of β -cyclodextrin (β -CD) and epichlorohydrin (Epi) in the presence of poly(vinyl alcohol) (PVA). The water soluble or hydrogel polymers were obtained depending on the β -CD/Epi molar ratios used in the polymerization. The structures of polymers were characterized by FT-IR, 1H-NMR, 13C-NMR, XRD, TGA, and DSC, respectively. The results demonstrated that the copolymerization between PVA and β -CD indeed occurred. The number of cyclodextrin units grafted on PVA chain calculated from 1H-NMR spectra are 37, 41 and 73 mole β -CD per 1000 mole PVA units in PVA-β -CD1, PVA-β -CD2 and PVA-β -CD3 polymers, respectively. The contents of β -CD in polymers increased with the increase of Epi/β -CD molar ratio in the reactions. In vitro release of aspirin (Asp) suggested that all polymers performed sustained-release of Asp, especially, PVA-β -CD3 showed nearly linear release of Asp for 24 h. The half lifetime of an Asp tablet made from PVA-β -CD 1∼ 5 is 13, 7, 13, 8, and 8 h, respectively. The 3-hydroxy-2-naphthoic acid (3H2NA) was used to study the interaction between drug and polymers. Fluorescence emission spectra analysis demonstrated that cyclodextrin units grafted on polymers keep the ability of forming inclusion complex with 3H2NA by supermolecular interactions. The regression of experimental data showed that 1:1 stoichiometry for the inclusion complex between β -CD and 3H2NA, and the association constant for PVA-β -CD1, PVA-β -CD2 and PVA-β -CD3 are 305, 97 and 354 mL· g−1, respectively, which increased with the increase of the content of β -CD in PVA-β -CD polymers.