3D printing and upcycling of bio-based polymers Pia S. Klee 1,2 , Clara Vazquez-Martel 1,2 , Lilliana Florido Martins 1,2 , Eva Blasco 1,2 1 Institute for Molecular Systems Engineering and Advanced Materials, Heidelberg University, Germany, 2 Organic Chemistry Institute, Heidelberg University, Germany 3D printing offers a great potential as a modern sustainable manufacturing technique for polymer materials. To fully exploit this potential three key aspects must be considered in the design: relying on renewable feedstocks, implementing valuable end-of-life options such as re- or upcycling and applying green chemistry principles. 1 While a lot of research has been done in finding bio-based alternatives to conventional fossil-sourced monomers, the latter two aspects have thus far often been overlooked in the design of sustainable polymers, despite being equally important. 2 Herein, lactate esters with different substituents were exploited as readily available bio-based molecules for the synthesis of 3D-printable monomers. By following green chemistry principles, a solvent-free, one-pot approach with a reusable catalyst was established for the monomer synthesis while achieving high conversions at mild conditions. In combination with a recycled crosslinking unit, an 3D printable ink formulation based on the lactate ester monomers was optimized for digital light processing (DLP). The resulting printed structures displayed geometries with high resolution. As an end-of-life strategy for the printed structures, an upcycling process relying on an aminolysis reaction was developed, yielding a pre-cursor of the same crosslinker used in the ink formulation which could in turn was incorporated into further ink formulations, introducing a material circularity into the system. Therefore, the strategic design of a system for light-based 3D printing that incorporates the three key objectives for creating sustainable polymers could successfully be demonstrated. References 1. E. Sanchez-Rexach, T. G. Johnston, C. Jehanno, H. Sardon and A. Nelson, Chem. Mater. , 2020, 32 , 7105–7119. 2. D. E. Fagnani, J. L. Tami, G. Copley, M. N. Clemons, Y. D. Y. L. Getzler and A. J. McNeil, ACS Macro Lett. , 2021, 10 , 41–53.
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