Micro-heterogeneity and micro-rheological properties of cellulose-based hydrogel studied by diffusing wave spectroscopy (DWS)

Authors: Xu, Jingyuan - James; BODDU, VEERA - Us Environmental Protection Agency (EPA); Kenar, James - Jim

Submitted to: Cellulose Chemistry and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2024
Publication Date: 3/1/2024
Citation: Xu, J., Boddu, V.M., Kenar, J.A. 2024. Micro-heterogeneity and micro-rheological properties of cellulose-based hydrogel studied by diffusing wave spectroscopy (DWS). Cellulose Chemistry and Technology. 58(1-2), 1-7. https://doi.org/10.35812/CelluloseChemTechnol.2024.58.01.
DOI: https://doi.org/10.35812/CelluloseChemTechnol.2024.58.01

Interpretive Summary: Cellulose is the most plentiful biopolymer and is a natural, biodegradable and inexpensive biomaterial. It can be processed into aqueous-based gels, hydrogels. Hydrogels have many applications such as water absorption material for coating agricultural seeds, drug delivery systems, wound-healing materials, and cosmetic gels. ARS researchers in Peoria, Illinois prepared cellulose-based hydrogels through modification of cellulose with a biobased organic acid. In order to identify potential applications of this cellulose-based hydrogel, the physical properties of the gel (micro-heterogeneity and micro-rheological properties) are investigated using a technical approach named Diffusion Wave Spectroscopy. We discovered unique concentration dependent properties. This research provides more insight into the physical properties of the hydrogel which may be useful for developing new food and non-food applications.

Technical 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 novel 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 the diffusing wave spectroscopy (DWS). The mean-square displacement (MSD) of microspheres imbedded into CHCCA hydrogels prepared at five concentrations were 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 "The magnitude of complex moduli is proportion to [frequency]", which is characteristic of a viscoelastic fluid-like behavior. The magnitude of high-frequency viscoelastic moduli for 0.3wt% and 0.5wt% CHCCA can be described by "The magnitude of complex moduli is proportion to [frequency]^3/4", which is characteristic of a semi-flexible polymer. The high-frequency viscoelastic moduli magnitude for 1.0wt% and 1.5wt% CHCCA described by "The magnitude of complex moduli is proportion to [frequency]^1/2", which was characteristic of a flexible polymer. Our results identified unique CHCCA property changes that occurred with changes in concentration and provides new insights for CHCCA derived hydrogels that will be useful in developing new CHCCA applications.