Vat Photopolymerization of Supersoft Acrylamide-Based PDMS Bottlebrush Elastomers

Bottlebrush polymers, defined as polymers densely grafted with polymer side chains, have gained much attention for their unique mechanical properties. When cross-linked into a bottlebrush polymer network, these materials exhibit moduli in the kilopascal range, significantly softer than conventional linear polymer networks. The ability to access these “super-soft” materials creates exciting opportunities in fields requiring biointerfacing or highly compliant materials, such as tissue engineering, biomedical devices, and pressure sensors. Additive manufacturing (AM), specifically vat photopolymerization (VPP), provides a platform for the fabrication of a polymer network with precise and bespoke form factors. However, challenges such as high resin viscosity and slow curing rates are known obstacles for integrating bottlebrush polymer chemistry into VPP processes. This study introduces a synthetic approach leveraging acrylamide-terminated poly(dimethylsiloxane) (PDMS) macromonomers and cross-linkers for the VPP manufacturing of supersoft, solvent-free elastomers. These siloxane-based resins exhibit both low viscosity and rapid photocuring, making them ideal materials for VPP. The cross-link density can be directly controlled through formulation design, achieving storage moduli from 10³ to 10⁶ Pa, without necessitating solvent or plasticizer as in conventional systems. The elastomeric response of the photocured materials is evaluated with compression testing, reversibly accessing strains of up to 60%. The quality of the 3D-printed parts is confirmed via scanning electron microscopy. This work offers a practical synthetic route to 3D-printable PDMS-based supersoft elastomers, with modulus values on the order of soft tissue, for next-generation sensors and biointerfacing technologies.