ACCESSING SALOPLASTIC BEHAVIOR IN CHITOSAN-CNC POLYELECTROLYTE COMPLEXES

Mixing oppositely charged polyelectrolytes can lead to the formation of Polyelectrolyte Complexes (PECs). The mechanical properties of these complexes are dependent on the ionic crosslinking between the polymers, which is influenced by factors such as polymer characteristics, pH, and ionic strength. By modifying the ionic crosslinks through the addition of a electrolytes, it is possible to induce a ‘plasticization’ process termed ‘saloplasticity’,¹ allowing for the reshaping of the complexes and the adjustment of their mechanical properties.² Furthermore, the use of natural polymers to create composite PECs, such as chitosan and cellulose nanocrystals (CNC), offers an alternative to non-biodegradable materials, promoting the development of more sustainable options.

In this work, we investigate the complexation of high molar mass chitosan and sulfated CNC under different conditions to produce pH- and ionic strength-responsive saloplastic hydrogels and films. For a microscopic approach, layer-by-layer (LbL) films of chitosan and CNC were obtained by sequential flow deposition onto gold sensors and monitored in situ using a Quartz Crystal Microbalance with Dissipation (QCM-D). In a macroscopic approach, Chitosan:CNC films (1:1 charge stoichiometry) were produced by solvent casting and annealed with NaCl solutions at different concentrations. The elastic (E’) and viscous (E’’) moduli, as well as tan δ, were evaluated using Dynamic Mechanical Analysis (DMA). An increase in E’’ and tan δ was observed with rising NaCl concentrations, indicating saloplastic behavior in the Chitosan:CNC complexes.

References

1. Porcel, C. H. & Schlenoff, J. B. Biomacromolecules 10, 2968–2975 (2009).
2. Shamoun, R. F., Reisch, A. & Schlenoff, J. B. Adv Funct Mater 22, 1923–1931 (2012).

Acknowledgement: The authors thank FAPESP for funding this project (grant number 2021/12701-6) and for providing the G. Vedovello PhD scholarship (grant number 2023/07740-1).