Fig. 1. Highly entangled polyacrylamide hydrogels have crosslinker-independent mechanical properties before light exposure. (A) Schematic representation of the formation of entangled polyacrylamide networks using PEG-diPDA (photodegradable diacrylate, red) and PEG-diAcm (non-degradable diacrylamide, blue) crosslinkers. (B) Representative tensile stress–strain curves of tanglemers prepared with each crosslinker, strained at 10 percent per second. (C) Mechanical properties of diPDA- and diAcm-crosslinked tanglemers including (i) Young's modulus, (ii) strain to failure, (iii) strength and (iv) work of fracture. (D) Hydrogels exhibit negligible hysteresis regardless of crosslinker identity. (E) Tensile stress–strain curves under active irradiation (shaded region) beginning at 250% strain show photoresponsiveness in diPDA-crosslinked hydrogels only. n = 3–4 gels per condition, with representative data shown in panels (B), (D), and (E).
