Chitosan (CS) is a polysaccharide known to have many interesting biological properties (biocompatibility, bioresorbability, antibacterial and antifungal activity…)[1]. The production of chitosan fibers could be useful for many biological applications but would need an improvement of the mechanical properties to allow shaping process, for instance fabric knitting, to develop biomedical textile implants.[2,3]

If nature is able to produce high mechanical properties fibrous structural materials like chitin, cellulose, silk, this is often thanks to the incorporation of rigid crystalline blocks in a soft matrix [4]. There are many examples, in nature, of nano-crystallites embedded in an amorphous matrix (e.g. cellulose nano-crystals within a cellulose/hemicellulose/lignin matrix in wood, chitin nano-crystals in chitin/protein/CaCO3 in crustaceans cuticle, beta-sheet pseudocrystallites in silk fibers…).

Thus, increasing the number of crystallites in spun chitosan fibers, i.e. the proportion of rigid blocks within the amorphous matrix, is a well-known approach to enhance the mechanical properties of CHI fibers to achieve biomedical knittable textile fabrics.

One possibility to increase the chitosan crystallinity index (CrI), and thereby its fiber mechanical properties, could be by optimizing the molecular mass of chitosan polymer. In this work we explored the influence of a molecular mass bimodal distribution by producing fibers made from mixed dopes of CS of high molecular mass (HMw) that should maintain a mechanical strength and CS of low molecular mass (LMw) that could increase the number of nucleation points and then chitosan crystallinity. Both films and fibers were produced with different proportions of LMw chitosan, and the influence of this proportion on: (i) the CHI crystalline microstructure and preferential orientation was characterized by X-ray synchrotron scattering WAXS (ESRF, Grenoble) as well as on (ii) the mechanical properties of the spun LMw/HMw chitosan fibers by uniaxial tensile test characterization (textile tenacity, strain at break, Young’s modulus).

[1] I.Aranaz, A.R. Alcantara, M.C. Civera, B. Elorza, A. Heras Caballero, N. Acosta. Polymers 2021, 13 (19)

[2] S. Marquez Bravo, I. Doench, P. Molina, F.E. Bentley, A.K. Tamo, R. PAssieux, F. Lossada L. David, A. Osorio-Madrazo, Polymers 2021, 13 (10), 1563

[3] R. Passieux, G. Sudre, A. Montembault, M. Renard, A. Hagege, P. Alcouffe, A. Haddane, M. Vandesteene, N. Boucard, L. Bordenave, L. David, ACS Biomater Sci Eng. 2022

[4] N.A. Yaraghi D. Kisailus, Annu. Rev. Phys. Chem. 2018, 69 (1), 23–57