Suprarmolecular hydrogels based on low-molecular-weight poly(ethylene glycol) and α-cyclodextrin

摘要

In previous studies, crystalline precipitates, not stable hydrogels, were obtained when low-molecular-weight (MW) poly(ethylene glycol) (PEG; weight-average MW = 400-5000) was used to interact with α-cyclodextrin (α-CD). In this study, the gelation ability of low-MW PEG (number-average MW = 2000, PEG-2000) and α-CD was systematically investigated through the variation in the concentration of PEG-2000 in water (C_(PEG-2000)) and the feeding molar ratio of the PEG repeat unit to α-CD (R). The results show that a stable supramolecular hydrogel could be constructed when C _(PEG-2000) was kept at 40 mg/mL and R was 6.3. The inclusion complexation between α-CD and PEG-2000 and the effect of C PEG-2000 and R on the stability of the hydrogels were characterized by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and rheology measurements. The resulting PEG-2000-based hydrogels retained the basic characteristics of supramolecular physical hydrogels, especially the property of shear thinning.