STUDY OF RHEOLOGICAL PROPERTIES OF HYDROGELS BASED ON OXIDIZED NANOCELLULOSE DERIVATIVES

166 Volume 5, Issue 10: Special Issue (EJAR) ISSN: 2181-2020 MPHAPP THE 6TH INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE “MODERN PHARMACEUTICS: ACTUAL PROBLEMS AND PROSPECTS” TASHKENT, OCTOBER 17, 2025 in-academy.uz STUDY OF RHEOLOGICAL PROPERTIES OF HYDROGELS BASED ON OXIDIZED NANOCELLULOSE DERIVATIVES Urishova F.M. Kuzieva M.M. Abitkhudjaeva Z.R. Atakhanov A.A. Institute of Polymer Chemistry and Physics, Academy of Sciences of Uzbekistan, 100128, Tashkent city, Republic of Uzbekistan e-mail: [email protected] https://doi.org/10.5281/zenodo.17328710 Nowadays, nanocellulose (NC) derivatives are used in various high-quality functional applications. One of them is oxidized nanocellulose, which is used in the biomedical and pharmaceutical fields due to its biodegradable, biocompatible, hemostatic and antibacterial properties. We synthesized oxidized nanocellulose (ONC) via potassium permanganate (KMnO₄) oxidation and investigated the rheological properties of ONC-based hydrogels. Rheological characterization provides essential insights into the mechanical integrity and stability of hydrogels. Both frequency sweep and amplitude sweep experiments were conducted to evaluate the viscoelastic performance of ONC hydrogels. These tests allow differentiation between solid-like and liquid-like behavior, determination of the linear viscoelastic region (LVE), and identification of the yield point, where the internal network collapses. In frequency sweeps, a stable gel is defined by a frequency-independent storage modulus (G′) dominating over the loss modulus (G″). All ONC hydrogels exhibited G′>G″ throughout the frequency range, confirming their predominantly elastic character. In contrast, MCC showed a relatively high damping factor (tanδ≈0.9), consistent with weak elasticity and viscous predominance. Oxidation markedly enhanced network strength: ONC-2 displayed improved elasticity, while ONC3h achieved the highest G′ values (10⁴–10⁵ Pa) and the lowest tan δ (~0.1–0.2), characteristic of a strong, stable gel network stabilized by carboxyl groups. ONC-4, however, exhibited declining G′ at higher frequencies, indicative of network fatigue and partial breakdown caused by cellulose chain scission during prolonged oxidation. Amplitude sweeps further clarified the strain-dependent stability of gels. Within the LVE, both G′ and G″ remained constant, reflecting intact networks; beyond this region, G′ decreased and eventually crossed G″ at the yield point. MCC hydrogels displayed a narrow LVE and early yielding (γ≈15–20%), highlighting poor resistance to deformation. ONC-2 extended the LVE slightly (~20– 25%), whereas ONC-3 showed the broadest LVE (~25–30%) and the highest G′ plateau, exemplifying a “true gel” with excellent stability under deformation and strong cohesive forces. ONC-4 again yielded earlier (~15–20%) with reduced moduli, confirming the detrimental effects of excessive oxidation [1]. Taken together, both rheological tests demonstrate that ONC-3 hydrogels strike the optimal balance between functionalization and structural integrity. They combine frequency-independent elasticity, a broad LVE, and high yield strain — hallmarks of robust gel networks. In contrast, ONC2 and ONC-4 deviate from this profile due to insufficient and excessive oxidation, respectively. These findings are highly relevant for the design of nanocellulose-based hydrogels tailored to biomedical applications such as mucoadhesion, drug delivery, and wound healing.