Using cellulose nanofibers to reinforce polysaccharide films: Blending vs layer-by-layer casting

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Polysaccharide films like alginate (Alg) and chitosan (CH) are widely studied for various applications.
• Incorporating reinforcing additives can enhance the mechanical and barrier properties of these films.
• Cellulose nanofiber (CNF) is a promising nanomaterial for reinforcing polymer matrices due to its high strength and surface area.

Purpose of the Study:

• To investigate the effect of cellulose nanofiber (CNF) as a reinforcing additive on the properties of alginate (Alg) and chitosan (CH) films.
• To compare the performance of CNF-reinforced films fabricated by blending and layer-by-layer (LbL) methods.
• To understand the underlying mechanisms, including electrostatic interactions, governing the CNF-polysaccharide matrix interactions and their impact on film characteristics.

Main Methods:

• Fabrication of Alg and CH films with varying concentrations of CNF using blending and LbL techniques.
• Characterization of film mechanical properties (tensile strength), barrier properties (water vapor permeability), and optical properties (opacity).
• Microstructural analysis (SEM) to observe CNF dispersion, and spectroscopic techniques (FTIR, DSC) to confirm interactions between CNF and polysaccharides.

Main Results:

• CNF addition significantly increased the tensile strength of Alg films and LbL CH films, with the highest TS reaching 140 MPa for blending Alg film at 7 wt% CNF.
• CNF-reinforced films generally exhibited lower water vapor permeability compared to unreinforced films.
• CNF addition increased film opacity, particularly in blending methods. CNF dispersion was good in Alg films but showed aggregation in blending CH films.
• FTIR, DSC, zeta-potential, and turbidity analyses confirmed electrostatic interactions between CNF and polysaccharides, correlating with observed film performance.

Conclusions:

• Cellulose nanofibers effectively reinforce alginate and chitosan films, enhancing mechanical strength and barrier properties.
• The fabrication method (blending vs. LbL) and the specific polysaccharide influence CNF dispersion and overall film performance.
• Electrostatic interactions play a crucial role in the successful integration of CNF into polysaccharide matrices for improved material properties.