SYNTHESIS OF QUATERNARY AMMONIUM CHITOSAN IN IONIC LIQUID

Abstract

In this study, 1-butyl-3-methylimidazolium chloride (BMIMCl) was used as a solvent for synthesis of positive-charged chitosan derivatives, N,N,N-trimethylammonium chitosan chloride (TMC), N-[(2-hydroxyl-3-trimethylammonium) propyl]chitosan chloride (HTCC), N-butyl-N-[(2-hydroxyl-3-trimethylammonium) propyl]chitosan chloride (NB-HTCC) and N-octyl-N-[(2-hydroxyl-3-trimethylammonium) propyl]chitosan chloride (NO-HTCC). The degree of quaternization (DQ) of the charge derivatives were calculated from NMR analysis. It was found that chitosan dissolved completely in BMIMCl after 16 h of heating at 90°C. The optimized reaction condition of TMC synthesis gave a maximum DQ of 40%, which was lower than the original method of using NMP as reaction media (75%DQ). It was possible that water from aqueous NaOH/NaI caused the chitosan polymer to precipitate in the reaction mixture, retarding the reaction. For HTCC compounds, the DQ of HTCC, NB-HTCC, and NO-HTCC were 87±4, 90±2 and 95±1 respectively. The synthesis of HTCC by using re-purified solvent (BMIMCl) was evaluated. For the most efficiency, it is recommended that BMIMCl should be re-used only once in the production of HTCC from chitosan. The antibacterial activity test for HTCC derivatives was carried out. HTCC, NB-HTCC and NO-HTCC had higher antibacterial activity against S.aureus (gram positive bacteria) than the original chitosan. This indicates that the positive charge on chitosan effectively improved the antibacterial activity of the polymer.