Fig. 3: Recoverable mechanical properties of the DIF fibers regulated by dynamic imine network.
From: Protein fibers with self-recoverable mechanical properties via dynamic imine chemistry
a Fatigue test of the 100% post-stretched DIF-72 fiber as an example. The fiber was alternatively stretched (20% strain) and relaxed for 2000 cycles. b Schematics illustrates the underlying mechanism for the recovery of fatigued DIF-72 fiber at pH = 8. Some imine bonds and hydrogen bonds were broken under repeated mechanical stretching, which could be repaired by immersing fibers in a pH = 8 aqueous solution with 50 mm Na3PO4 followed by air drying. c Stress-strain curves of original, fatigued, and recovered DIF-72 fibers. d Ultimate tensile strength and toughness of original, fatigued, and recovered DIF-72 fibers. Fatigued fibers essentially restored their mechanical performances after immersion at pH = 8 and re-dried in the air. e Stress-strain curves of the DIF-72 fibers immersed at pH = 7, 5, 3, 1 for 12 h and recovered at pH = 8 for 12 h. f Ultimate tensile strength and toughness of the post-stretched DIF-72 fibers under different pH treatments. The mechanical performances of post-stretched DIF-72 fibers were weakened as the pH decreased, which was recovered at pH = 8. The asterisks denote the statistical significance: *p < 0.05 and ****p < 0.0001. ns no significant difference. All data (d), (f) in the graphs are mean values of standard deviation (mean ± SD, n = 30). Statistical analysis was performed with GraphPad Prism 8.0 and Origin 2021 software. The results (d), (f) are obtained by the statistical approach of two-way t-tests.
