The main focus of this project is to study, on the molecular level, the motion of dye molecules during the formation of crosslinked polymers and in the resulting networks. For this purpose we will apply single molecule spectroscopy techniques such as fluorescence correlation spectroscopy and wide-field microscopy. Single dye molecules will be used as probes for detecting the freedom of molecules to move within the developing polymer network and for visualizing the microstructure of the produced material. Translational and rotational diffusion will be investigated as they can be used to probe different network densities. Special attention will be drawn to heterogeneities on the molecular scale developing during network formation. Translation and rotation are abundant in loose networks or at early stages of polymerization. However, as the network becomes denser, translation will subsequently slow down and the molecules will only have enough space to rotate. Eventually, as the network becomes still denser, rotation will also freeze and the motion of the molecules will stop completely. We hope to observe the opposite process during the degradation of polymers, a process which shall also be elucidated by our techniques. Furthermore, hydrogels that have considerable practical significance e.g. in contact lenses and plastic implants, will be investigated. The dynamics related to their swelling behaviour, which is rather poorly understood at present, is of particular interest. Structural characterization of the systems is essential and will be primary done by IR and Raman spectroscopy.
