Tailor-making molecular optical force probes for polymeric materials

• Maßgeschneiderte molekulare optische Kraftsonden für polymere Materialien

Baumann, Christoph; Herrmann, Andreas (Thesis advisor); Möller, Martin (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

Research on material properties enables continuous improvement of known materials and the design of new, innovative, and interactive matter. In particular, the response of materials to mechanical forces is an important area of research to prevent their failure and increase material robustness. Therefore, the molecular mechanisms underlying mechanical fracture must be understood. Nevertheless, to understand the complex interdependent processes at the molecular level, new tools have to be established. In this thesis, force-sensitive molecules, so-called mechanophores, are therefore developed and used as force probes, providing new insights into materials. Beforehand, the performance of an already developed system, an extended anthracene-maleimide Diels-Alder adduct, as a force probe was demonstrated. In several collaborative projects, new methods to increase the detection sensitivity were presented, and different types of materials were explored. By studying regioisomers of this mechanophore in relation to polymer attachment points, first insights regarding the mechanochemical reactivity depending on the position of the polymer attachment have been obtained, and thus a foundation for the development of new mechanophores was provided.Subsequently, based on these Diels-Alder adducts, a new design of symmetric mechanophore with high adaptability, due to an exchangeable aromatic core, was developed. The optical properties of the design were varied and explored by introducing different aromatic systems. In particular, a development of dual fluorescent mechanophores with benzothiadiazole and with naphtothiadiazole cores enabled coverage of the complete visible light spectrum and allowed simultaneous local quantification of broken and non-broken bonds. Moreover, another mechanophore design combining a highly discussed triazole motif with the Diels-Alder motif was presented, allowing an easy synthesis and its incorporation at the interface of polymers via “click” reactions.