Enhanced antimicrobial activity and reduced water absorption of chitosan films graft copolymerized with poly(acryloyloxy)ethyltrimethylammonium chloride

Chitosan shows selective antimicrobial activity as a bioactive polymer. In this work, a quaternary ammonium derivative of chitosan was synthesized by graft-copolymerization of chitosan with poly[2-(acryloyloxy)ethyltrimethylammonium chloride] or pATC by the redox polymerization method to enhance chitosan's antimicrobial activity. The structural characterizations of the quaternized chitosan were confirmed by Fourier transform infrared spectroscopy, and also by 1H and 13C nuclear magnetic resonance spectroscopy. The produced chitosan was converted into films by solution casting. The physicomechanical properties of the modified chitosan were compared with the unmodified chitosan. Thermal stability of the films was characterized by thermogravimetric analysis. The pATC grafted chitosan films showed lower thermal stability, water absorption, swelling ratio, and tensile strength compared to the unmodified chitosan film. Antimicrobial activity of the quaternized chitosan was tested against three kinds of bacteria (Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa) and two fungi (Aspergillus brasiliensis and Aspergillus fumigatus). The unmodified chitosan showed good antibacterial activity but no resistance against any fungus. However, the pATC grafted chitosan showed enhanced antibacterial activity against all bacteria investigated. The fungicidal test shows that the pATC-grafted-chitosan showed higher activity against the tested fungi (Aspergillus fumigatus and Aspergillus brasiliensis) compared to the unmodified chitosan, especially against Aspergillus fumigatus.