Photophysical characterization of dynamically linked polymers for self-healing applications
The thesis at hand deals with the spectroscopic and photophysical characterization of dynamically linked polymers, so called dynamers. Dynamers have already found extensive use in the fields of sensor systems or self-healing materials, but the combination of their dynamic chemistry with optical properties such as absorption or emission is still an open field of research. The present thesis is divided in three main parts. First, dynamers that rely on the Diels-Alder functionality were investigated by steady-state and time-resolved, i.e. transient absorption and time-resolved emission, spectroscopies. The chromophores embedded in the polymer scaffold belonged to the class of oligo(arylene ethynylene)s, which are known for their pronounced emission properties. In particular, the influence of the dynamer structure on their ground- and excited state properties both in solution as well as in thin films was studied. Additionally, energy transfer experiments in different polymer compositions were conducted. Second, an imine based polymer was probed with regards to its photostability. Utilizing different excitation energies and solvent properties, different photochemical deactivation pathways were found. Last, an imine-based polymer system was investigated that could partially self-heal its absorption properties after photodamage. Different polymer sructures which affected polymer mobility in films were tested and general rules for the design of optically active self-healing polymers were derived. Keywords: dynamic polymers, dynamic chemistry, self-healing, time-resolved spectroscopy, transient absorption spectroscopy, energy transfer, arylene ethynylene, phenylene ethynylene, photoisomerization, photooxidation.