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

Hydrogels used for different applications meet specificrequirementsof mechanical properties, leading to complicated material and processdesign. Here we report a simple one-step method for achieving a seriesof transparent hydrogels with highly tunable properties through free-radicalphotopolymerization (FRPP) of a single monomer, inspired by the fundamentalmechanism of FRPP kinetics. The properties of poly-N-acryloyl 2-glycine (PNAG) hydrogels could be tailored within a rangeof 0.14 to 2.58 MPa tensile strength, 15 to 519 kPa Young'smodulus, and 33 to 2.8 x 10(3) g/g water-absorbing capacityby 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 highelasticity with low hysteresis under cyclic loading at low deformation.More intriguingly, the photochemical decomposition rate of photoinitiator1173 under UV-LED (365 nm) and the internal interactions of PNAG hydrogelswere found to be temperature-dependent, which may offer a promisingsupplement to the temperature effect theory in FRPP. This work notonly presents a new perspective for the design of hydrogels for aspecific application but also paves the way for more extensive cooperationbetween FRPP and other preparation methods.

Automated summary

A series of transparent hydrogels with highly tunable properties were achieved through a simple one-step method of free-radical photopolymerization (FRPP) using a single monomer. The properties of these hydrogels were adjusted by changing the polymer chain length and intermolecular interactions. The study also found temperature-dependence in the photoinitiator decomposition rate and internal interactions of the hydrogels, which could inspire further research in FRPP.