Structure induced changes of the optical properties of metallo-supramolecular polyelectrolytes incorporated into a polymer matrix

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In this project a new class of mechano-responsive polymer composites shall be explored in terms of their structure-property relationships. The components of the composites are based on metallo-supramolecular polelectrolytes (MEPEs) and on polymers. The MEPE acts as the mechano-responsive functional unit, while the polymer defines the viscoelastic properties of the composite. The hypothesis of the mechano-responsive effect in these composites is based on the assumption that a mechanical force will induce a change in the coordination environment of the MEPE thus resulting in a color-change. The first goal of the project is to synthesize defined composites that show a color change upon mechanical deformation. The second goal is to study the mechanism of the color change in detail and to verify the above-mentioned hypothesis. The coordination environment of the central metal ions will be characterized by spectroscopic methods such Raman-, X-ray fluorescence, and X-ray absorption-spectroscopy as function of composition and mechanical deformation. Integration of fluorescent groups allows analysis of small changes in the MEPE even at low concentrations by fluorescence spectroscopy. By the judicious choice of the ligands, metal ions and counter ions the MEPEs are readily modified in order to tune the interaction with the polymer matrix as well as the resulting mechano-chromic response.