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. Author manuscript; available in PMC: 2023 Oct 31.
Published in final edited form as: Chem Soc Rev. 2022 Oct 31;51(21):9127–9173. doi: 10.1039/d2cs00618a

Figure 5. Examples of slide-ring polymers to form hydrogels with improved toughness.

Figure 5.

(A) Molecular design of a hydroxypropylated polyrotaxane (HPR) crosslinker (HPR-C) based on α-cyclodextrin (α-CD) and (B) schematic of free radical copolymerization of N-isopropyl(acrylamide) (NIPA) and sodium acrylic acid (AAcNa) using the developed crosslinker. (C) Demonstration of highly stretchable and deformable hydrogels. (D) Stress-strain curves for (i) NIPA–AAcNa–N,N′-methylene-bis(acrylamide) (BIS) (0.65 wt%), (ii) NIPA–AAcNa–BIS (0.065 wt%), (iii) NIPA–AAcNa–HPR-C (2.00 wt%), (iv) NIPA–AAcNa–HPR-C (1.21 wt%) and (v) NIPA–AAcNa–HPR-C (0.65 wt%) shows the hydrogels containing the same amount of crosslinkers but different amounts of HPR-C crosslinker can stretch up to 912%, which is significantly higher than that of BIS crosslinker, (i.e., 29%). Reprinted by permission from ref 81. Nature Publishing Group, Copyright 2014. (E) Schematic illustration of the gelation via metal coordination through pseudo-polyrotaxanes. (F) The mechanism proposed for the thermal relaxation and shear-induced gelation effects. (G) Chain conformation changes with stretching the hydrogel, and (H) digital photographs of the hydrogel stretched by ~30×. Reprinted by permission from ref 84. Nature Publishing Group, Copyright 2019.