Supramolecular Polymerization of Photopolymer Enables Tough 3D Soft Objects

Light-based 3D printing remains to be the only technique able to build free-form 3D architectures in high resolution. By crosslinking photocurable monomers or macromonomers using UV light, layers of rigid polymer networks are formed to construct a 3D structure. Ever since its development, light-based 3D printing has continued improving printing speed and resolution through optimization of printing systems such as use of dead layers¹, flowing liquid interface² and two-photon polymerization³. Despite the advance in printability, the lack of photopolymers to print stretchable and durable elastomers has restricted further application of 3D printing to stretchable devices such as bio-implantable devices, E-skin, and soft robots.<br/>Here I present the supramolecular approach to toughen 3D printed elastomers. Our designed photopolymer includes supramolecularly polymerizable ‘sticker’ in their backbone, which spontaneously polymerize to form a preliminary network even before printing. Due to this supramolecular network, the printed elastomer network shows superior stretchability, compressive strength, toughness, fracture toughness, and fatigue threshold in one system. The key of this result reveals to be suppressing network defect formation. Even though defects are well known to weaken the mechanical properties of polymer networks, conventional photopolymers were not able to avoid defects due to the rapid process of 3D printing. In my presentation, I will discuss details of the design strategy and its toughening mechanism.<br/><br/>References<br/>1. Tumbleston, J. <i>et al. Science</i> <b>347,</b> 1349-1352 (2015)<br/>2. Walker, D. <i>et al. Science</i> <b>366,</b> 360-364 (2019)<br/>3. Zhang, W. <i>et al. Nat. Commun.</i> <b>12,</b> 112 (2021)