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

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 cross-linking 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 cross-linked 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.