Fig. 4: Stability and reliability of the DIF fibers under extreme conditions.

a Schematics show the treatments of 100% post-stretched DIF-72 fibers under cold (cooling in liquid nitrogen at −196 °C for 12 h) conditions. b, c The ultimate tensile strength (b) and toughness (c) of post-stretched DIF-72 fibers at −196 °C for 12 h show no obvious decrease in mechanical performance after low-temperature treatment. ns no significant difference. All data (b, c) in the graphs are mean values of standard deviation (mean ± SD, n = 30). The result (b) is obtained by the statistical approach of F-tests. The result (c) is obtained by the statistical approach of two-way T-tests. d Schematics show the treatments of 100% post-stretched DIF-72 fibers under hot conditions (heating in an oven at 100, 150, and 200 °C for 12 h), and tested ex-situ at room temperature (RT). e, f The ultimate tensile strength (e) and toughness (f) of post-stretched DIF-72 fibers at ex-situ high temperatures (100, 150, and 200 °C) for 12 h. These values are only slightly decreased when heated at 100 and 150 °C in the system. When further increasing temperature to 200 °C, the mechanical performance of DIF-72 fibers was reduced significantly. All data (e, f) in the graphs are mean values of standard deviation (mean ± SD, n = 30). g Schematics showing the treatments of 100% post-stretched DIF-72 fibers by in situ high-temperature tests by DMA. h, i The ultimate tensile strength (h) and toughness (i) of post-stretched DIF-72 fibers at in situ high temperatures (100, 150, and 200 °C). The asterisks denote the statistical significance: *p < 0.05, ***p < 0.001, and ****p < 0.0001. All data (h, i) in the graphs are mean values of standard deviation (100 °C, mean ± SD, n = 9; 150 °C, mean ± SD, n = 8; 200 °C, mean ± SD, n = 7). Statistical analysis was performed with GraphPad Prism 8.0 and Origin 2021 software. The results (b, c), (e, f), (h, i) are obtained by the statistical approach of two-way t-tests.