A Solvent-Free Photochemical Route to Clickable Multifunctional Polyacrylic Elastomers

Multifunctional polyacrylic elastomers with ultrastrechability, hydrophobicity, self-healing, and adhesive properties have wide applications in wearable electronics, sensors, soft robotics, and biomedical science. However, it is challenging to integrate these functionalities into one material in a simple solvent-free approach. To address this challenge, we herein develop a two-step bulk photopolymerization method to make ultrastretchable, adhesive, self-healable, hydrophobicity-tunable elastomers by adding a small amount of 1-ethynylcyclohexyl acrylate (ECA) into a common acrylate, ethyl acrylate. ECA efficiently prevents uncontrollable solidification during the first step photopolymerization and acts as a cross-linker to make elastomers in the second step photocuring. When ECA increases from 0.5 to 3.3 mol %, the maximum strain of elastomers decreases from 3087 to 1763% and the maximum stress increases from 0.19 to 1.04 MPa. These elastomers show a peeling strength of 1233–1621 N/m when adhering to different surfaces, including glass, steel, and polymethyl mathacrylate . They can self-heal to its original modulus with a fracture strain of 1100% and fraction stress of 0.5 MPa. In addition, we can use surface photoclick thio-yne reactions to tune the hydrophobicity with contact angles from 113° ± 2° to 79° ± 2°. We believe that our environmental-friendly solvent-free approach toward multifunctional polyacrylate elastomers will expand their applications in various areas.