Compartmentalization in soft matter is important for segregating and coordinating chemical reactions, sequestering (re)active components, and integrating multifunctionality. Advances depend crucially on quantitative 3D visualization in situ with high spatiotemporal resolution. Here, we show the direct visualization of different compartments within adaptive microgels using a combination of in situ electron and super-resolved fluorescence microscopy. We unravel new levels of structural details and address the challenge of reconstructing 3D information from 2D projections for nonuniform soft matter as opposed to monodisperse proteins. Moreover, we visualize the thermally induced shrinkage of responsive core-shell microgels live in water. This strategy opens doors for systematic in situ studies of soft matter systems and their application as smart materials.

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.

To realize carriers for drug delivery, cationic containers are required for anionic guests. Nevertheless, the toxicity of cationic carriers limits their practical use. In this study, we investigate a model system of polyampholyte N-isopropylacrylamide (NIPAM)-based microgels with a cationic core and an anionic shell to study whether the presence of a negative shell allows the cationic core to be shielded while still enabling the uptake and release of the anionic guest polyelectrolytes. These microgels are loaded with polystyrene sulfonate of different molecular weights to investigate the influence of their chain length on the uptake and release process. By means of small-angle neutron scattering, we evaluate the spatial distribution of polystyrene sulfonate within the microgels. The guest molecules are located in different parts of the core-shell microgels depending on their size. By combining these scattering results with UV-vis spectroscopy, electrophoretic mobility and potentiometric titrations we gain complementary results to investigate the uptake and release process of polyelectrolytes in polyampholyte core-shell microgels. Moreover, Brownian molecular dynamic simulations are performed to compare the experimental and theoretical results of this model. Our findings demonstrate that the presence of a shell still enables efficient uptake of guest molecules into the cationic core. These anionic guest molecules can be released through an anionic shell. Furthermore, the presence of a shell enhances the stability of the microgel-polyelectrolyte complexes with respect to the cationic precursor microgel alone.

Die nanoskopische In-situ-Bildgebung weicher Polymerstrukturen ist fürd as Verständnis der Zusammenhänge von Struktur,Eigenschaften und Funktionalitätimnm-Bereich entscheidend. Die Vernetzung von Polymerketten legt die viskoelastischen Eigenschaften eines Gels fest, und die Korrelation zwischen mechanischen Eigenschaften und der Verteilung und Menge an Vernetzern ist fürA nwendungen und ein elementares Verständnis von Polymeren auf der molekularen Ebene relevant. Hier wird eine auf superauflçsender Fluoreszenzmikroskopie basierende Methodik zur Visualisierung und Quantifizierung von Vernetzungspunkten in Polymersystemen vorgestellt. Ein neuartiger Diarylethen-Photoschalter mit stark fluoreszierender geschlossener und nicht-fluoreszierender offener Form wird als photoschaltbarer Vernetzer in ein Polymernetzwerk eingebaut. Seine photophysikalischen Eigenschaften, sein Schaltverhalten und seine hohe Photostabilität machen ihn zu einem idealen Kandidaten fürp hotoaktivierte Lokalisationsmikroskopie.A ls Anwendungsbeispiel wurden pNIPAM-Mikrogele untersucht, die bekanntlichh ohe Variationen in ihrer internen Vernetzungsdichte aufweisen.

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