Structural and rheological properties of chitosan semi-interpenetrated networks

The local structure and the viscoelastic properties of semi-interpenetrated biopolymer networks based on cross-linked chitosan and poly(ethylene oxide) (PEO) were investigated by Small Angle Neutron Scattering and rheological measurements. The specific viscosity and the entanglement concentration of chitosan were first determined, respectively, by capillary viscosimetry and steady-state shear rheology experiments performed at different polymer concentrations. Mechanical spectroscopy was then used to study the gelation process of chitosan/PEO semi-interpenetrated networks. By fitting the frequency dependence of the elastic and loss moduli with extended relations of relaxation shear modulus around the sol-gel transition, it was shown that the addition of PEO chains had a significant effect on the viscoelastic properties of aqueous chitosan networks but no effect on the gelation time. The improvement of mechanical properties was in accordance with the correlation length decrease deduced from Small Angle Neutron Scattering experiments.