MICRO-HETEROGENEITY AND MICRO-RHEOLOGICAL PROPERTIES OF CELLULOSE-BASED HYDROGEL STUDIED BY DIFFUSING WAVE SPECTROSCOPY (DWS)

Abstract

Cellulose is the most plentiful biopolymer available in the world, and is a natural, biodegradable as well as inexpensive resource for biomaterials. Herein, a cellulose-based superabsorbent hydrogel (CHCCA) was prepared by crosslinking carboxymethyl cellulose (CMCNa) and hydroxyethyl cellulose (HEC) with citric acid, and its micro-heterogeneity and micro-rheological properties were explored by diffusing wave spectroscopy (DWS). The mean-square displacement (MSD) of microspheres imbedded into CHCCA hydrogels prepared at five concentrations was compared. At very low concentration, of 0.1wt%, the CHCCA hydrogel exhibited nearly homogeneous behavior, with slight heterogeneity. The heterogeneity became larger as the CHCCA concentration increased. It was also revealed that the high-frequency viscoelastic moduli magnitude at 0.1wt% CHCCA can be expressed by |G*(ω)| ∝ ω, which is characteristic of a viscoelastic fluid-like behavior. The magnitude of high-frequency viscoelastic moduli for 0.3 wt% and 0.5 wt% CHCCA can be described by |G*(ω)| ∝ ω3/4, which is characteristic of a semi-flexible polymer. The high-frequency viscoelastic moduli magnitude for 1.0 wt% and 1.5 wt% CHCCA described by |G*(ω)| ∝ ω1/2, was characteristic of a flexible polymer. Our results identified unique CHCCA property changes that occurred with changes in concentration, providing new insights for CHCCA derived hydrogels that will be useful in developing new CHCCA applications.