Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was ...performed at 80-100 °C as verified by Fourier transform infrared (FT-IR). The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min) were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured), chemically cross-linked (cured), and uncross-linked (prepared by acetic acid) films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs) on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials.
Here we investigated the chitosan (CS)–graphene oxide (GO) supramolecular scaffold and the significant synergistic effect of GO and carbon nanotubes (CNTs) in the structure. To this end, a ...supramolecular hydrogel was prepared by fulfilling the conditions for intermolecular self-assembly between GO nanosheets and CS chains. Also, CS-wrapped CNTs were incorporated into the system to induce electrical conductivity. Then, the structure was developed to a macroporous scaffold through subsequent lyophilization. The formed architectures were characterized by using dynamic mechanical thermal analysis (DMTA), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), field emission scanning electron microscopy (FE-SEM), and wide angle X-ray diffraction (XRD). The results indicated that the combination of CNTs and GO nanoparticles has a synergistic effect on the distribution and performance of the two nanoparticles. Due to the amphiphilic nature of CS, the presence of each of the nanoparticles improves the interaction of CS with the other, resulted in improving their dispersion into the biopolymeric matrix. Supramolecular properties, convenience and ease of preparation of the scaffolds make them suitable for applications such as biomedical engineering, biosensors, and artificial muscle, especially for cardiac tissue engineering due to their electrical conductivity and high porosity.
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