Photocuring Three-Dimensional Printing of Thermoplastic Polymers Enabled by Hydrogen Bonds

The advent of 3D printing has led to a new era of highly customized products. Printing reprocessable thermoplastic polymers is limited to slow printing techniques such as fused deposition modeling. Photocuring 3D printing is a high-speed 3D printing technique suitable for photocurable thermosetting resins because the cross-linked 3D network could achieve rapid solid-liquid separation during printing. However, thermoplastics usually cannot be printed via photocuring 3D printers because rapid solid-liquid separation is hard to be achieved due to the diffusion/dissolution of linear molecular chains in their liquid precursor. Herein, we hypothesize that hydrogen bonds (H-bonds) between monomers may accelerate polymerization and reduce solubility of the polymer in liquid precursors to achieve rapid solid-liquid separation. Using this strategy, a series of UV-curable methacrylic and acrylic monomers was selected as inks to demonstrate the role of H-bonds in photocuring 3D printing. The hypothesis was further verified by using blended inks of N-vinyl-2-pyrrolidinone (NVP) and acrylic acid (AA) via experimental and molecular dynamic simulation. Oil palm occupies the top position of plantation species in southeastern Asian forests. Palm oil (PO) has the lowest price compared with other plant oils. Thus, a PO-based vinyl monomer was selected as the raw material for 3D printing thermoplastic polymers. Various biobased thermoplastics were successfully printed from the PO-based monomer and commercial monomers. The amide structure in the PO monomer formed H-bonds with polar monomers, including NVP and AA, resulting in printed 3D objects with surprising functionalities such as high stretchability and self-healing ability.