Synthesis of polyvinyl alcohol/chitosan hydrogels and ınvestigation of their swelling and degradation behaviors in various pH environments

Hydrogel-based biomaterials offer significant advantages in biomedical applications, including high biocompatibility, tunable mechanical properties, and controlled drug release. In this thesis, polyvinyl alcohol (PVA) and chitosan-based composite hydrogels were synthesized using the freeze-thaw method with varying chitosan concentrations and four different freeze-thaw cycles. Their swelling and degradation behaviors were investigated and compared under various pH conditions. The physical and chemical properties of the hydrogels were characterized using SEM and FTIR analyses. The results demonstrate that chitosan concentration, pH level, and freeze-thaw cycles significantly influence swelling capacity and degradation rates. SEM analysis revealed structural changes associated with increasing chitosan content and the impact of pH on degradation. It was determined that the degree of crosslinking increased with the number of freeze-thaw cycles. Additionally, SEM results confirmed that crosslinking led to a compatible composite structure between PVA and chitosan polymers. FTIR analysis indicated that degradation in acidic environments was more pronounced compared to basic conditions. An increase in chitosan concentration was found to significantly enhance swelling ratios. Hydrogels containing 10% chitosan exhibited a swelling ratio of 875% at pH 2, whereas those containing 50% chitosan reached up to 1899%. Furthermore, higher swelling ratios were observed in acidic environments compared to basic conditions. Hydrogels containing 30% chitosan and subjected to a single freeze-thaw cycle exhibited a swelling ratio of 1280% at pH 2 and 742% at pH 12. Degradation tests revealed that hydrogels generally exhibited higher degradation rates in acidic environments than in basic ones. An increase in chitosan concentration also resulted in higher degradation rates. Hydrogels containing 50% chitosan exhibited a degradation rate of 35% at pH 2 and 10% at pH 12, while those containing 10% chitosan showed degradation rates of 12% at pH 2 and 6% at pH 12. A strong correlation was also observed between swelling and degradation rates. The effects of chitosan concentration, pH level, and freeze-thaw cycle number on swelling and degradation behaviors were successfully modeled using artificial neural networks (ANN) in MATLAB with high accuracy.