Chitosan (Qs) is a biopolymer with promising potential in biomedical applications. However, under physiological conditions, it exhibits mechanical and barrier limitations due to the weak intermolecular and intramolecular interactions inherent to its molecular structure. There is increasing interest in enhancing these properties by modifying the biopolymer with clays and/or natural cross-linking agents. In this study, the physical properties of chitosan were modified by incorporating bentonite (Be). The biocomposite materials were obtained by casting and prepared with varying percentages of Be (CSC, CSBe15, CSBe25, CSBe35, and CSBe45). Biofilms with good flexibility and adhesion were successfully developed and characterized by FTIR, WAXS, SAXS, TGA, and DSC. FTIR analysis confirmed the protonation of the Qs -NH₂ groups and the formation of hydrogen bonds (O-H/N-H band) at 3430 cm⁻¹. A band at 2941 cm⁻¹ and a shift in the C=O peak indicated cross-linking within the chitosan polymer chains, while the band at 1000 cm⁻¹, corresponding to Si−O bond vibrations, confirmed the presence of Be. WAXS and SAXS analyses revealed clay intercalation (d ≈ 1.8 nm) with no evidence of exfoliation. Thermogravimetric analysis (TGA) showed improved thermal stability: neat chitosan (CSC) exhibited a T₁₀ of 121.47 °C, whereas Be-containing biofilms showed T₁₀ values ranging from 122.64 to 137.95 °C. Swelling tests in physiological saline revealed a 40% increase in swelling with the incorporation of Be; however, as Be content increased, the swelling capacity decreased. This suggests that bentonite acts as a secondary cross-linking agent, binding to chitosan chains through intermolecular forces, thereby enhancing the properties of pure chitosan. Preliminary bacteriological studies indicate a promising potential for these materials in biomedical applications.

The support from SECITHI through the doctoral scholarship awarded to Y.L.R.R. is gratefully acknowledged. Likewise, special thanks are extended to Dr. Jesús Ortiz Palacios, Research Professor in the Department of Engineering at CU Costa Sur (University of Guadalajara), for his invaluable guidance, and to Dr. Omar Felipe Fabela Sánchez, affiliated with the Department of Macromolecular Chemistry and Nanomaterials at CIQA , for his co-supervision and support during the development of this research project. The characterization of the materials was conducted at CIQA, whose facilities and technical support were essential to this study.