Materials with programmable properties controlled by light

Disclosed are methods, compositions, reagents, systems, and kits to prepare materials with viscoelastic properties that respond to irradiation with light. Various embodiments show that bio-inspired histidine:transition metal ion complexes allow precise and tunable control over the viscoelastic properties of polymer networks containing these types of crosslinks pre and post-irradiation. These materials have the potential to aid biomedical materials scientists in the development of materials with specific stress-relaxing or energy-dissipating properties.