269: Development of polymer networks containing tethered weak bonds

Development of polymer networks containing tethered weak bonds

Charlène Breton¹, Danish Equbal¹, Thomas Hooper², Dimitrios Sakellariou², Charles-André Fustin¹ 

¹UCLouvain, Institute of Condensed Matter and Nanoscience - Bio and Soft Matter division (IMCN-BSMA) Louvain-la-Neuve, Belgium

²KULeuven, Membrane Separation, Adsorption, Catalysis, and Spectroscopy for Sustainable Solutions (cMACS), Leuven, Belgium

charlene.breton@uclouvain.be

For several decades, biological materials, such as mollusk byssus, have been a source of inspiration to develop a new class of stiff and tough materials with self-repair capacity.¹ These properties are often related to the presence of sacrificial bonds releasing hidden length.¹ While giving interesting properties to the network, weak bonds have major drawbacks (lower mechanical strength, bad shape persistence, e.g.) due to an overall lower strength and faster dynamics. Therefore, developing a strategy to exploit weak bonds while limiting their drawbacks presents a strong interest.

Even though the concepts of sacrificial bond and hidden length have been explored in several materials such as elastomers or hydrogels^2,3, their use has not yet been exploited to its full potential due to the mostly empirical approaches used to develop these materials.⁴ In this project our aim is to investigate in depth the impact of inserting tethered weak bonds into polymeric materials. The studied networks rely on metallo-supramolecular weak bonds connected by an oligo (ethylene glycol) linker.

Here, we present the development of an “ideal” model network based on 4-arm star poly(ethylene glycol) linked by tethered metal-ligand coordination bonds. We develop first the design and synthesis strategies for obtaining such network using a terpyridine-based crosslinker. Then, we use a combination of solid-state and DQ-NMR to gain insight into the composition and structure of the network. Finally, we highlight the dynamic behavior of the metal-ligand bonds through rheological and mechanical measurements.

 References

1) Zhou, X., Guo, B., Zhang, L. & Hu, G.-H. Progress in bio-inspired sacrificial bonds in artificial polymeric materials. Chem. Soc. Rev. 46, 6301–6329 (2017).

2) Ducrot, E., Chen, Y., Bulters, M., Sijbesma, R. P. & Creton, C. Toughening Elastomers with Sacrificial Bonds and Watching Them Break. Science 344, 186–189 (2014).

3) Nakajima, T. Generalization of the sacrificial bond principle for gel and elastomer toughening. Polym. J. 49, 477–485(2017).

4) Creton, C. 50th Anniversary Perspective: Networks and Gels: Soft but Dynamic and Tough. Macromolecules 50,8297–8316 (2017).