Orientation of Chitin Nanofibers Dispersed in a Thermoplastic Polymer Matrix Through Dry Thermal Stretching

Abstract

Nanostructures derived from structural polysaccharides, such as cellulose and chitin, are notable for their sustainability, lightweight properties, and superior mechanical attributes. The macroscopic performance of these materials largely depends on the orientation of nanostructures. This study explores the preferential orientation of chitinous nanofibers (NFs) within a thermoplastic polymer matrix (PM) comprising poly(N-vinylpyrrolidone) and glycerol, achieved through dry thermal stretching techniques. Altering the PM composition enables the modulation of the system's glass transition temperature (T_g). Chitin NFs are effectively dispersed within the PM, with their orientation enhanced by stretching at temperatures ≈30 °C above the T_g of the composites, resulting in an elongation at rupture (ε) of 105%. Under similar temperature conditions, composites with chitosan NFs show strong interactions with the PM, hindering the stretching process (ε = 10%). In contrast, composites with acetylated chitin NFs demonstrate increased stretchability (ε = 170%) but have insufficient interactions to stabilize their orientation. These interactions, identified as hydrogen bonds through FTIR, vary significantly based on the functional groups present on the NF surfaces. This variation is supported by DSC and dynamic mechanical analysis. Oriented ChNFs hold potential for bioactive applications.