Solution plasma process for deacetylation and depolymerization of chitin hydrogel

Abstract

In this study, solution plasma process (SPP), a plasma generated in a liquid phase, was applied in depolymerization and deacetylation reactions of chitin hydrogel to form chitosan. Chitin hydrogel, an amorphous form of chitin, was depolymeried by SPP in 1% acetic acid solution for 0 h, 3 h, and 5 h in order to reduce its molecular weight before being subjected to deacetylation reaction to form chitosan. The effect of depolymerization prior to deacetylation on the degree of deacetylation (DD) of the deacetylated products was examined. Deacetylation reaction was performed by applying SPP in different concentrations of KOH in MeOH. The concentrations of KOH in MeOH were varied to be 0%, 7%, and 10%. Deacetylation reaction via SPP was done repeatedly up to 5 cycles (one hour for each cycle to achieve the highest values of %DD). The effects of KOH concentration and plasma treatment time on %DD, molecular weight, chemical structure, and crystallinity of the deacetylated products were investigated by FTIR, GPC, and XRD. The results showed that %DD determined by FTIR increased with an increasing of the KOH concentration and plasma treatment time. In addition, the depolymerization of chitin hydrogel prior to deacetylation resulted in the higher values of %DD and %solubility of the deacetylated products.