Additive Manufacturing of Molecular Architecture Encoded Stretchable Polyethylene Glycol Hydrogels and Elastomers

Polyethylene glycol (PEG) networks are widely used in biomedical applications and are emerging as solid-state polymer electrolytes for next-generation lithium batteries. Leveraging additive manufacturing technologies, such as digital light processing (DLP), PEG networks can be transformed into micro-architected metals and functional biomimetic vascular networks. However, developing stretchable PEG networks, let alone making them 3D printable, remains a fundamental challenge. Here, DLP printable, highly stretchable foldable bottlebrush PEG networks are reported. These networks are formed by rapid photopolymerization of low-cost commercial chemicals in ambient air. The bottlebrush architecture enables high molecular weight PEG network strands that do not crystallize and remain elastic without solvents at room temperature. Upon large deformation, the folded bottlebrush backbone unfolds to release stored length to enable extreme stretchability. The resulting hydrogels and elastomers exhibit tissue-like moduli ranging from ≈1 to ≈100 kPa and tensile breaking strains up to 1500%. The applications of bottlebrush PEG networks are demonstrated as matrices for highly stretchable and conductive solvent-free polymer electrolytes at room temperature (≈900% strain and 1.2 mS cm^-1), as well as resins for DLP printing of complex architectures, cytocompatible organ-like geometries, functional devices, and multi-material structures with seamless interface integration. The developed photocurable bottlebrush PEG networks promise immediate applications in advanced (bio)manufacturing and beyond.