Digital Light Processing of Dynamic Bottlebrush Materials

Bottlebrush elastomers have attracted significant attention as a class of super-soft materials with a storage modulus (G ') less than the intrinsic entanglement shear modulus (G(e)), but current processing strategies have been limited to molding or extrusion-based 3D printing. Here, the ability to 3D print bottlebrush elastomers via digital light processing (DLP) is demonstrated through the design of novel resin components and building blocks. In particular, mono-telechelic poly(ethylene glycol) (PEG) macromonomers with a 1,2-dithiolane end group derived from alpha-lipoic acid (LA) undergo fast and efficient copolymerization with PEG diacrylates under light (<= 405 nm) in the presence of a photoinitiator to generate crosslinked bottlebrush networks containing dynamic disulfide backbones. This allows objects that are both super-soft and solvent-free to be printed with a commercial DLP printer. The resulting materials undergo dynamic disulfide exchange when exposed to ultraviolet light (365 nm) or elevated temperatures, facilitating reprocessing and postfabrication healing. These results establish a simple design strategy for the preparation of DLP resins based on natural building blocks (alpha-lipoic acid), leading to materials with unique properties that broaden the utility of light-based 3D printing with user-friendly chemistry.