Graded Metallopolymer Structures with Shape‐Memory Abilities via DLP‐Based 3D‐Printing

ABSTRACT In this study, for the first time, the digital light processing (DLP) based 3D printing of graded metallopolymer structures is presented. Herein, the individual segments are based on the combination of terpyridine‐ and triphenylmethyl(trt)‐histidine‐based monomers crosslinked with zinc(II) and nickel(II) salts, respectively. Subsequently, photopolymerization with 2‐phenoxyethyl acrylate as a comonomer is conducted using the same printing conditions for all mixtures. At defined times, the resin mixtures are exchanged, leading to graded structures. Prior to this study, it was not possible to access such graded materials based on the segmented combination of chemically different metal complexes. Temperature‐dependent Raman spectroscopy is utilized to investigate the materials with a special focus on the interface between the different segments. Here, a narrow dynamic region at the intersection, thinner than one printing layer (about 20 µm), was detected. The implemented metal‐ligand combinations can be thermally activated and enable excellent shape‐memory abilities, without the need for switching via the glass transition temperature. Furthermore, the permanent shape can be recovered in two steps, and thermo‐mechanical analysis measurements revealed excellent shape fixities (close to 100%) and overall recovery rates (as high as 99%).