Self-Healing Supramolecular Hydrogel Made of Polymers Bearing Cholic Acid and β-Cyclodextrin Pendants

Abstract

Natural compounds cholic acid and β-cyclodextrin are attached separately as pendant groups in a copolymer with N, N ′-dimethylacrylamides. The formation of supramolecular hydrogels is induced by inclusion complex formation between cholic acid and β-cyclodextrin moieties as evidenced by rheological analysis and 1 H NMR spectroscopy. Storage modulus of the hydrogel shows a maximum value when the molar ratio of cholic acid to β-cyclodextrin units is adjusted to 1:1. The concentration of the hydrogel can be as low as 5.5 wt %. Both shear-thickening and shear-thinning have been observed when the shear rate gradually increases from 0.01 to 100 s –1 . The inclusion complexation renders the gel–sol process reversible under heating and cooling cycles. The self-healing of such hydrogels is observed and confirmed by step-strain rheological measurements. The dynamically reversible host–guest complexation provides reasonably good mechanical properties of the cross-linked polymer network. The natural origin of the constituents may make the hydrogels suitable candidates for biomedical applications pending further tests.