Room-Temperature 3D Printing of a Super-Soft and Solvent-Free Elastomer

Super-soft elastomers derived from bottlebrush polymer networks show promise as advanced materials for biomimetic tissue and device applications, but current processing strategies are restricted to simple molding. Here, we introduce an alternative approach rooted in molecular design that enables direct ink write (DIW) 3D printing of super-soft bottlebrush elastomers at room temperature without solvent. The key advance is a new class of shear-thinning inks comprising statistical bottlebrush polymers that self-assemble into well-ordered body-centered cubic spheres at remarkably asymmetric compositions. These single-component soft solids undergo sharp and reversible yielding at 20 °C in response to shear with a yield stress and structural modulus that can be tuned by manipulating the length scale of microphase separation. Addition of a soluble photo-crosslinker containing benzophenone end-groups allows complete UV curing after extrusion to form super-soft elastomers (shear moduli ≈ 1–50 kPa) with unusual mechanical properties, namely near-perfect recoverable elasticity well beyond the yield strain. In summary, the unique bottlebrush polymer structure–property design rules elucidated herein create new opportunities to tailor the performance of super-soft elastomers in ways that are not possible with current materials and processes.