Polybutadiene Click Chemistry: A Rapid and Direct Method for Vat Photopolymerization

Abstract

Thiol−ene click chemistry was utilized to cross-link unmodified commercial liquid polybutadiene (PB) and complex geometries were 3D printed using vat photopolymerization. PB homopolymer contains pendent reactive moieties inherent to its synthesis which were used as crosslinking sites in a photosensitive resin without copolymerization or postpolymerization modification of the PB to include conventional photocurable moieties such as acrylates. Thiols were found to preferentially react with pendent olefinic units, and the mechanical properties of crosslinked specimens generally behaved as expected, that is, an increase in the cross-link density led to an increase in tensile stress but a decrease in strain at break. Resins were downselected for printability and working curves were obtained, showing evidence of a "dark cure" attributed to the thiol−ene reaction's relative insensitivity to oxygen. Objects with challenging structures were printed by using commercial digital light processing printers.

Vat Photopolymerization of Synthetic Isoprene Rubber Latexes

“…Despite the commercial availability of silicone elastomers − and segmented polyurethanes, − the integration of diene-based rubbers remains in nascent stages within the realm of 3D printing. The literature has explored various strategies for cross-linking diene-based rubbers, including traditional free radical polymerization from methacrylated polyisoprene precursors and thiol–ene reactions involving thiol cross-linkers and pendant double bonds on poly­(1,3-butadiene). , The incorporation of reactive diluents in low-molecular-weight diene-based rubbers effectively reduced the viscosity to the levels amenable for VP. However, employing low-molecular-weight diene-based rubbers as precursors for their low viscosity led to inferior ultimate stress or strain at break as compared to elastomers prepared from high-molecular-weight polymers.…”