Customization of Supramolecular Hydrogels through One-Step Photopolymerization and Its Mechanism

Abstract

Hydrogels used for different applications meet specific requirements of mechanical properties, leading to complicated material and process design. Here we report a simple one-step method for achieving a series of transparent hydrogels with highly tunable properties through free-radical photopolymerization (FRPP) of a single monomer, inspired by the fundamental mechanism of FRPP kinetics. The properties of poly-N-acryloyl 2-glycine (PNAG) hydrogels could be tailored within a range of 0.14 to 2.58 MPa tensile strength, 15 to 519 kPa Young’s modulus, and 33 to 2.8 × 103 g/g water-absorbing capacity by adjusting the polymer chain length and intermolecular interactions. The strongest PNAG hydrogel, with a tensile strength of 2.58 MPa, could be stretched to 14 times its original length and showed high elasticity with low hysteresis under cyclic loading at low deformation. More intriguingly, the photochemical decomposition rate of photoinitiator 1173 under UV-LED (365 nm) and the internal interactions of PNAG hydrogels were found to be temperature-dependent, which may offer a promising supplement to the temperature effect theory in FRPP. This work not only presents a new perspective for the design of hydrogels for a specific application but also paves the way for more extensive cooperation between FRPP and other preparation methods.