Structure–Property Relationships of Acrylate-Terminated Polybutadiene as a Photocurable Elastomer for Additive Manufacturing

Abstract

Additive manufacturing (AM) is widely used in the medical, automotive, and prototyping industries due to its ability to print complex geometries. Multiple AM modes employ photopolymerization to fabricate an array of cross-linked polymer networks. Here, we use ring-opening metathesis polymerization to synthesize hydroxyl-terminated polybutadiene (HTPB) with control over molecular weight and hydroxyl functionality, while maintaining low dispersity. We then modified these HTPB samples to produce acrylate-terminated polybutadiene (ATPB), which combines the photocurable characteristics of acrylates with the material flexibility and elasticity of the polybutadiene backbone. Using a library of ATPB oligomers with systematic variations in molecular weight (Mn = 3–11 kg/mol) and acrylate functionality (f = 3–20), we identified key structural parameters that modulate the glass-transition temperature (Tg) and cure kinetics. The ATPB oligomers were then incorporated into photopolymerizable resin formulations and evaluated for cure kinetics, thermomechanical properties, and the ability to be printed into multilayer, complex structures with suitable resolution. Due to its fast cure rate and low Tg, ATPB with functionality 4 and Mn of ∼9 kg/mol was selected for further study. This formulation enabled successful 3D-printing via UV-assisted direct ink write (DIW) of complex geometries, with fumed silica added to improve print fidelity. Mechanical testing revealed isotropic behavior in the XY plane and demonstrated that the material’s compliant, rubbery properties are suitable in 3D-printed elastomeric applications.