under humid atmosphere for 6 h (Fig. 12b). Self-healing ability of hydrogels with
good mechanical properties (1,650 Pa) was also assessed by alternating strain test
(strain between 1 and 1,000%) where each strain was applied for 60 s. Hydrogel
regained its initial storage modulus instantly when stress was dropped (Fig. 12c).
Disappearance of the seam and uniform distribution of PEG-DOX conjugate owing
to the dynamic nature of hydrazone linkages also demonstrates self-healing.
While most of the reports utilize polymers with reactive groups at their chain
ends, it is also possible to employ polymers with reactive functional groups on their
side chains. Reversible addition fragmentation chain transfer (RAFT)
Fig. 11 (a) Hydrogel formation through acylhydrazone bond formation between PF127 aldehydes
and G3, (b) tensile test curves of the original hydrogel (black curve) and the hydrogel self-healed for
24 h (red curve). Adapted with permission [28]. Copyright 2017, American Chemical Society
Self-Healing Hydrogels Based on Reversible Covalent Linkages: A Survey of. . .
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