Metallopolymers as multifunctional and multistimuli-responsive shape-memory materials

• Applicant: Professor Dr. Ulrich S. Schubert
• Subject Area: Polymer Materials
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 317854808

Shape-memory polymers are able to recover their original shape after preceded deformation. Upon an external trigger (e.g., heat) the polymer will return from the temporary shape into its initial shape. Metallopolymers are suitable candidates for the design of novel shape-memory polymers, which can be considered as the missing link between the established shape-memory polymers and shape memory alloys. Shape-memory metallopolymers are on-demand switchable shape-memory polymers. Due to the integrated supramolecular interaction (i.e. the metal-ligand-interaction) the reversibility (from low to high) as well as the suitable trigger (e.g., temperature, chemicals and redox reactions) can be tuned. Within the project, new metallopolymer networks with different metal ions (i.e. different potential triggers) and comonomers will be prepared. Within this context, two different processing methods will be utilized, i.e. reactive inkjet printing as well as copolymerization in bulk. The resulting metallopolymers will be investigated regarding their shape-memory behavior and the possibility to trigger the materials with different external stimuli like heat, light or chemicals. Furthermore, the influence of the chosen metal salt on the resulting properties as well as the addressability by the different stimuli will be studied in detail. This basic information will later be utilized for the design of novel triple-shape memory metallopolymers. For this purpose, two different types of metal complexes are required, which can be triggered independently from each other. Thus, one metal complex can be triggered to obtain a transition from the first temporary shape to the other one. Finally, the other metal complex will be addressed by the same stimulus at other conditions (e.g., higher temperature) or by the utilization of a complete different stimulus (e.g., heat and light) resulting in the final permanent shape. In another part of the project the self-healing ability of the shape-memory metallopolymers will be studied. In this context, the influence of the shape-memory behavior on the self-healing behavior will be studied and will also be compared to the classical self-healing metallopolymers. Thus, it will be investigated if there is a shape-memory assisted self-healing (SMASH). Finally, a completely new shape-memory behavior will be studied, which is the multiway triple shape-memory behavior. For this purpose, a metallopolymer with two independently addressable metal complexes is required. Furthermore, two different stimuli have to be utilized. In contrast to classical triple shape-memory polymers this new behavior offers the possibility to have two different temporary shapes after the applying of the first external stimulus depending on the order of the utilized stimulus. Thus, if light is applied first a completely different shape will be obtained. Finally, if the other stimulus is also used the permanent shape will be obtained.

• DFG Programme: Research Grants