Fig. 4: Solvent resistance of TPOU and CPOU fibers.

a Photographs of dissolution tests of TPOU and CPOU fibers. (i) Fibers were immersed in THF at room temperature; (ii) after 5 min, TPOU fiber dissolved, while CPOU fiber kept intact. b Photographs of dried CPOU fiber after swelling with THF: (i) lifting an object, (ii) 2.5 times stretched, and (iii) recovered within 1 min.