SKM 2023 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster Session II

CPP 35.59: Poster

Wednesday, March 29, 2023, 11:00–13:00, P1

Adaptive Air-Water Interfaces with Spiropyran and Arylazopyrazole Photoswitches — •Michael Hardt and Björn Braunschweig — University Münster, Center for Soft Nanoscience, 48149 Münster, Germany

Interfaces that respond to stimuli such as light or temperature are of great interest for new intelligent materials. Using molecular switches that respond to orthogonal triggers, the properties of fluid interfaces can be preconditioned and a low level of adaptivity can be integrated that extents the possibilities of soft matter interfaces beyond responsive functions.
In this contribution, we report on the adaptive behavior of air-water interfaces that are decorated by spiropyran (SP) and arylazopyrazole (AAP) photo-responsive surfactants. The SP surfactants increase their surface activity when irradiated with UV light that causes a ring-closure reaction. E/Z photo-isomerization of the AAP surfactants drives a substantial decrease in surface activity and thus desorption from the interface when the AAP surfactants are switched from their E to the Z state. In addition, at low pH the short thermal lifetime of the Z state as well as of the SP form offers the use of thermal relaxation as an alternative trigger, while also irradiation with green light can partially recover the initial properties. Interfacial properties and molecular kinetics were studied in detail using surface tensiometry and vibrational sum-frequency generation (SFG).