Rheological Properties of Oxidised Cellulose Derivative Solutions

Sodium carboxymethyl cellulose (Na-CMC) and its oxidised derivative, dialdehyde carboxymethyl cellulose (DCMC), are increasingly relevant in biomedical, pharmaceutical, and cosmetic applications because of their biocompatibility and tunable rheological properties. While the rheological behaviour of Na-CMC solutions has been extensively characterised in the literature, the flow properties of DCMC - synthesised through periodate oxidation of Na-CMC - remain poorly understood. In particular, previous studies have been limited to narrow concentration ranges (0.5-1%) and temperature windows (30–50℃), and the influence of acetal and hemiacetal covalent linkages - formed during periodate oxidation - on viscous flow activation energy has not been systematically investigated across varying degrees of oxidation. To address these gaps, this study systematically investigates the rheological properties of DCMC solutions with oxidation degrees ranging from 34% to 82% at concentrations of 0.5-2.5 wt% over a temperature range of 25-40℃, with unmodified Na-CMC as a reference material. Key findings show that DCMC has a higher activation energy for viscous flow ($E_η$ = 32.15 kJ/mol) than Na-CMC ($E_η$ = 28.34 kJ/mol), indicating that acetal and hemiacetal cross-links significantly strengthen the polymer network. All tested DCMC solutions showed gel-like behaviour $(G^'>G^{''})$, confirming that oxidation-induced structural modifications preserve and enhance the material’s viscoelastic integrity. These results provide a quantitative molecular-level basis for tailoring DCMC properties in the design of hydrogels and controlled-release formulations for biomedical use.

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