Hydrogel of Radiation-Induced Cross-Linked Hydroxypropylcellulose

Abstract

Hydroxypropylcellulose (HPC) hydrogel being a material of natural origin, combines the properties of a polymer, which make up the network, with biodegradability. In this report the effects of high energy radiation on the ether of cellulose-HPC are presented. The polymer irradiated in its solid state or in dilute aqueous solution underwent mainly degradation, induced by the cleavage of glycosidic bonds in its main chain. Irradiation of HPC in aqueous solutions at moderate concentrations resulted in the formation of hydrogels. Chemical cross-links bond the chains of polymer, turning it to an insoluble macroscopic gel. We have found that in addition to concentration, dosage and dose rate can affect the results of irradiation. Electron beam irradiation gave higher gel fraction, up to 90%, than gamma irradiation, which has a maximum gel fraction of 65%. Swelling of the cross-linked hydrogels was related to the density of cross-links and was the highest at low irradiation doses. HPC hydrogels displayed thermally reversible character in their swelling. The volume of gel underwent continuous deswelling with an increase of the solution temperature, with the deswelling rate increasing rapidly over 40°C. At elevated temperatures the hydrogel collapsed, lost its transparency and changed color to translucent white. This transition was fully reversible when the gel was placed in the medium of low temperature. The hydrogel demonstrated superior mechanical properties. Despite of the stable three-dimensional cross-linked network, the gels underwent biodegradation under controlled conditions when enzyme was used.