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Supporting Information NMR spectra1D and 2D NMR spectra were recorded on a Bruker Avance III spectrometer, operating at 400.1, 100.6 and 40.6 MHz for 1 H, 13 C and 15 N nuclei, respectively. Samples were recorded with either

In the context of increasing interest in biomaterials with applicability in cosmetics and medicine, this research aims to obtain and characterize some hybrid materials based on chitosan (CS) (antibacterial, biocompatible, and biodegradable), poly(ethylene glycol) (PEG) (non-toxic and prevents the adsorption of protein and cell) and Laponite® RD (Lap) (bioactive). The rheological properties of the starting dispersions were investigated and discussed related to the interactions developed between components. All samples exhibited gel-like properties, and the storage modulus of CS/PEG dispersion increased from 6.6 Pa to 657.7 Pa by adding 2.5% Lap. Structural and morphological characterization of the films, prepared by solution casting method, was performed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and polarized light microscopy (POM). These analyses proved the incorporation of Lap into CS/PEG films and revealed the morphological changes of the films by the addition of clay. Thereby, at the highest Lap concentration (43.8%), the “house of cards” structure formed by Lap platelets, which incorporate chitosan chains, as evidenced by SEM and POM. Two stages of degradation between 200 °C and 410 °C were evidenced for the films with Lap concentration higher than 38.5%, explained by the existence of a clay-rich phase (given by the clay network) and chitosan-rich one (due to the intercalation of chitosan in the clay network). CS/PEG film with 43.8% Lap showed the highest swelling degree of 240.7%. The analysis of the obtained results led to the conclusion that the addition of clay to the CS/PEG films increases their stability in water and gives them greater thermal stability.

The present paper focuses on the rheological behaviour of a series of hydrogels prepared from chitosan and salicylaldehyde. The unusual crosslinking of chitosan with this monoaldehyde was assessed by 1H NMR spectroscopy, which demonstrated the formation of covalent imine bonds. The hydrogels exhibited a super-porous morphology, evidenced by SEM measurements, and the layered supramolecular structure of the hydrogels was sustained by the birefringence texture of the hydrogels, observed by polarized light microscopy (POM). The hydrogel-like behaviour was confirmed by rheologic measurements for the sample containing the highest salicylaldehyde amount. The dynamic flow properties of salicyl-imine-chitosan hydrogels with different crosslinking degrees (NH2/CHO ratios between 2 and 4) were investigated at temperatures in the range of 20–40 °C. The rheological moduli were determined over a wide range of oscillatory frequencies and the experimental results were presented using master curves. In addition, the thixotropic behaviour of the hydrogels based on chitosan and salicylaldehyde was determined and discussed. The measurements of thixotropy were performed by increasing the shear rate to 400 s-1 in an upward sweep, followed by its decreasing in a downward sweep. It was noticed that the hydrogels’ thixotropy increases with an increasing crosslinking degree. In line with this rheological behaviour, the self-healing ability was tested, and it was proved that the hydrogels were able to reshape after applying deformation stress.

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