Glycerol plasticisation of chitosan/carboxymethyl cellulose composites: Role of interactions in determining structure and properties.

Biopolymers such as chitosan and cellulose continue to attract much interest as they have many appealing characteristics such as biodegradability, biocompatibility, chemical versatility and natural functionality; however, many of their properties usually require further tailoring for specific purposes. This study shows that glycerol plasticisation and the addition of graphene oxide (GO) or reduced graphene oxide (rGO) altered the properties of chitosan and a chitosan/carboxymethyl cellulose (CMC) blend. For the chitosan/CMC matrix, GO or rGO was likely to disrupt polyelectrolyte complexation (PEC) between the two biopolymers, leading to weakened mechanical properties and increased surface hydrophilicity. Conversely, glycerol assisted PEC by increasing the biopolymer chain mobility, leading to reduced surface hydrophilicity. Moreover, some synergistic effects from a combination of glycerol and GO/rGO were evident. Specifically, GO/rGO notably increased the toughness of the chitosan film on inclusion of 40 wt% glycerol. Both GO and rGO reduced the relaxation temperatures of the chitosan/CMC film with 20 wt% glycerol added, resulting in increased biopolymer chain mobility. Moreover, the bionanocomposites showed high relative permittivity (54-387). Thus, this work describes how complex interactions in multiphasic biopolymer composite systems influence structure and properties.