Polyelectrolyte Complexation of Chitosan and WS₂ Nanotubes

The inclusion of tungsten disulphide nanotubes (WS₂ NTs) in chitosan, plasticized with glycerol, facilitates the formation of a polyelectrolyte complex. The glycerol interrupts the intramolecular hydrogen bonding between chitosan chains allowing positively charged protonated amines of chitosan to form a complex with negatively charged oxygen ions chemisorbed to the tungsten atoms in defects. These interactions, with the unique mechanical and chemical properties of WS₂ NTs, result in a chitosan film with superior properties relative to unfilled chitosan. Even at low WS₂ NT loadings (≤1 wt%), the Young's modulus (E) increases by 59%, tensile strength (σ) by 40% and tensile toughness by 74%, compared to neat chitosan, without sacrificing ductility. Addition of highly dispersed WS₂ NTs significantly improves the gas barrier properties of chitosan, with a 50% reduction in oxygen permeability, while the addition of both glycerol and WS₂ NTs to chitosan effectively reduces the carbon dioxide permeability by 80% and the water vapor transmission rate by 90%. The intrinsic antimicrobial efficacy of chitosan against both Gram-positive and Gram-negative bacteria is enhanced on inclusion of WS₂ NTs. Polyelectrolyte complexation of WS₂ NTs and glycerol-plasticized chitosan provides a cost-effective, sustainable route to biodegradable films with desirable mechanical, gas barrier properties, and antimicrobial efficacy suitable for food packaging applications.