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.
Microgels enable reversible stabilization of liquid crystal (LC) emulsions in ways that facilitate analysis of LC droplets that undergo an analyte-triggered conformational transition.
Thiophene NH-sulfoximines have been synthesized using a one-pot NH-sulfoximidation reaction of thiophenes. The reactivity of the products was investigated, and the developed protocols were used for the synthesis of a new class of dithienylethene-type photoswitches containing a sulfoximidoyl group.
Microgels are deformable polymer-networks with conspicuous properties. Their surface- activity associated with their switchability makes their application in liquid-liquid systems, such as extraction processes, particularly promising. For their application as switchable stabilizers at the interface, a detailed understanding of their impact on process relevant phenomena, such as the sedimentation behavior, is necessary. So far, the focus of research has been on microscopic-scale properties, whereby the propagation to macroscopic effects has rarely been quantified. In this study, single microgel-covered n-butyl acetate drops rising in a quiescent continuous water phase are investigated experimentally. The dependency of the microgel properties, in terms of size and cross-linking density, on the fluid dynamics are addressed. The impact of microgels is studied in detail by sedimentation velocity, drop deformation and the resulting drag coefficient. The deformation of drops is related to shape conserving interfacial properties such as the interfacial tension. Counter to our expectations, microgel-covered drops deform less than the drops of the pure system although microgels reduce the interfacial tension. Moreover, the sedimentation velocity is of special interest, since it reveals the mobility of the interface and friction conditions at the interface. Our results demonstrate the correlation between microgel properties at the interface on a microscopic scale and the macroscopic behavior of microgel-covered drops.
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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