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Chitosan is a semicrystalline natural polymer whose structural organization is strongly influenced by intermolecular hydrogen bonding, hydration, and preparation conditions [1, 2]. Incorporation of carbon-based nanomaterials, particularly thermally reduced graphene oxide (trGO), can substantially modify the molecular packing and crystalline ordering of the polymer matrix. In this work, the structural features of pure chitosan and chitosan-based composites with different trGO concentrations are investigated using X-ray diffraction (XRD), with infrared (IR) and Raman spectroscopy considered as complementary methods for characterizing molecular interactions and local structural changes.
XRD analysis reveals that pure chitosan exhibits a semicrystalline structure characterized by broad diffraction maxima at 2θ ≈ 9.4° and 21.2°, together with several relatively sharp crystalline reflections. The diffraction pattern is consistent with the coexistence of ordered crystalline domains and disordered regions, with possible contributions from hydrated and anhydrous structural forms [1, 2].
The incorporation of trGO leads to significant changes in the diffraction patterns. At low filler concentrations (1–4 wt.%), additional reflections appear near 2θ ≈ 14° and 17°, accompanied by broadening of the main diffuse maximum at 20–21°. These changes suggest a rearrangement of the polymer chains and a reduction in crystalline ordering, potentially associated with intermolecular interactions between chitosan and trGO. At a trGO concentration of approximately 10 wt.%, the emergence of a diffraction contribution near 2θ ≈ 25.4° indicates the development of graphene-rich domains and increased structural heterogeneity. Further increases in filler concentration promote the formation of a more complex multiphase structure.
IR and Raman spectroscopy provide complementary means of investigating the vibrational characteristics of chitosan, particularly the functional groups involved in hydrogen bonding and their possible interactions with graphene-based components. Their correlation with XRD results can help distinguish changes in molecular interactions from modifications of crystalline packing.
The obtained XRD results demonstrate that the incorporation of trGO substantially affects the structural organization of chitosan, leading to a concentration-dependent transformation from a predominantly polymer-ordered system toward a heterogeneous composite structure. Combined diffraction and vibrational spectroscopy studies can provide a more comprehensive understanding of the relationship between molecular interactions and structural ordering in chitosan-based materials.
This work was partly supported by NASU (RSW of young scientist №12/04-2025) and the National Research Foundation of Ukraine (Project № 2023.03/0012).
References
[1] K. Ogawa, T. Yui, M. Miya, Biosci. Biotechnol. Biochem. 56, 858–862 (1992). https://doi.org/10.1271/bbb.56.858.
[2] K. Okuyama, K. Noguchi, M. Kanenari et al., Carbohydr. Polym. 41, 237–247 (2000). https://doi.org/10.1016/S0144-8617(99)00142-3.
[3] K. Kosowska, P. Domalik-Pyzik, M. Nocuń, J. Chłopek, Mater. Chem. Phys. (2018). https://doi.org/10.1016/j.matchemphys.2018.05.076.
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