polymerization of acrylic monomers can give desired polymers and stimuliresponsive polymeric networks as demonstrated in the recent study by Zheng and
coworkers [31]. A ketone-based acylhydrazone bond containing self-healing hydrogel for local drug delivery was reported to reduce the cytotoxicity caused by reactive
aldehyde functional groups on gel precursors. Copolymer was obtained by RAFT
polymerization of diacetone acrylamide and acrylamide (DAAM/AM), and hydrogel
was synthesized by cross-linking the ketone-bearing polymer with hexanedihydrazide in DI water (Fig. 13a). Rheological tests were carried out to assess
self-healing property by continuous strain test. Under low strain (1%), material
showed gel-like behavior, while under high strain (1,500%) it turned into a sol
state. Upon reducing strain to 1%, G
0 immediate recovery was observed, and the
process was shown to be repeatable (Fig. 13b).
Fig. 12 (a) Preparation of PEG hydrogels from eight-arm PEG glyoxylic aldehyde and eight-arm
PEG hydrazine, (b) self-healing characteristic of two hydrogel halves (with and without PEG-DOX
loading), (c) G
0 at alternating strains of 1 and 1,000%. Adapted with permission [30]. Copyright
2019, American Chemical Society
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R. Kilic and A. Sanyal