HETEROGENEOUS SULFATION REACTIONS OF LOW MOLECULAR WEIGHT CHITOSAN

UDC 547.458.6:541.6.66

Аннотация

In this study, the heterogeneous sulfation of low molecular weight chitosan (LMWC, Mw = 12.2 kDa, DP = 73, PDI = 1.25) using sulfuric acid in isopropanol medium was systematically investigated. A series of sulfated chitosan derivatives were synthesized under varying reaction parameters, including temperature (-30 to +5 °C), time (1–24 h), and H₂SO₄ molar ratios (1.0–8.0 mmol/mmol GlcNU). The molecular characteristics of the obtained products varied within a wide range: DP = 58-73, DS = 0.026–1.289, sulfur content = 0.51–14.16%, SO₃Na = 1.64–45.58%, with yields ranging from 10.12% to 80.12%. FTIR spectroscopy confirmed successful sulfation through characteristic -SO₃^- absorption bands at 1220, 1060, 987, and 814 cm^-1, indicating that sulfation predominantly occurred at the C-6 position of glucosamine residues via hydroxyl and amino groups. The optimal reaction conditions were determined to be 4.0 mmol/mmol H₂SO₄ per glucosamine unit at -20 °C for 12 hours, ensuring high DS values and minimal depolymerization. Elemental analysis supported FTIR findings and showed high correlation between reaction variables and functional group incorporation. These results demonstrate that controlled heterogeneous sulfation of LMWC in isopropanol is an effective method to produce water-soluble, highly substituted chitosan derivatives with preserved backbone integrity. The obtained derivatives are promising for further biomedical applications such as drug delivery, anticoagulant formulations, and bioactive coatings. This study provides a clear understanding of how reaction parameters influence structural and functional outcomes in chitosan sulfation chemistry.