The in situ nanoscopic imaging of soft matter polymer structures is of importance to gain knowledge of the relationship between structure, properties, and functionality on the nanoscopic scale. Cross-linking of polymer chains effects the viscoelastic properties of gels. The correlation of mechanical properties with the distribution and amount of cross-linkers is relevant for applications and for a detailed understanding of polymers on the molecular scale. We introduce a super-resolution fluorescence-microscopy-based method for visualizing and quantifying cross-linker points in polymer systems. A novel diarylethene-based photoswitch with a highly fluorescent closed and a non-fluorescent open form is used as a photoswitchable cross-linker in a polymer network. As an example for its capability to nanoscopically visualize cross-linking, we investigate pNIPAM microgels as a system known with variations in internal cross-linking density.
Keywords: cross-linker; microgels; photoswitch; soft matter; super-resolution fluorescence microscopy.
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