Figure 11.

Photodegradable and photoadaptable hydrogels based on radical processes. a) Reaction scheme for photodegradation of hydrogels containing disulfide or allyl sulfide linkages. b) A photoadaptable disulfide-crosslinked hydrogel is exposed to light while pressed against a textured surface, resulting in photoinitiated deformation. Scale bar 1.5 mm. Reproduced from Fairbanks et al.²²⁵ copyright (2011) American Chemical Society. c) Radical-mediated photodegradation requires lower concentration of photoactive species, allowing for the photodegradation of thicker monolithic samples. In this example, a 1 cm-thick hydrogel is degraded in approximately 1 min of irradiation (365 nm, 10 mW cm⁻²). Scale bar 5 mm. Reproduced from Brown et al.¹⁹² copyright (2017) Wiley.