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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 5: Wetting, Fluidics and Liquids at Interfaces and Surfaces I (joint session CPP/DY)

CPP 5.3: Talk

Monday, March 9, 2026, 10:15–10:30, ZEU/0260

Photoswitchable Arylazopyrazole Monolayers on Aluminum Oxide for Tunable Wettability — •Tim Blinzer, Christian Honnigfort, and Björn Braunschweig — Institute of Physical Chemistry and Center of Soft Nanoscience, University of Münster, Corrensstraße 28-30, Münster 48149, Germany

Smart surfaces that can change their wettability on demand are interesting for applications such as self-cleaning or microreactors. To tune the surface wettability, we functionalized aluminum oxide surfaces with arylazopyrazole (AAP) phosphonic acids using a Langmuir-Blodgett transfer. AAP molecules in the deposited monolayers undergo reversible E/Z photoisomerization driving changes in surface wettability. This was investigated as a function of surface coverage, where the responsiveness—i.e. the changes in molecular structure and in the apparent contact angle—was studied in detail. Here time-dependent sum-frequency generation (SFG) was used to obtain in situ information on the dynamic changes in monolayer upon E/Z switching with 520 nm green and 365 nm UV light. Furthermore, we show that increasing surface roughness by depositing nanoaggregates of the AAP phosphonic acid leads to a drastic increase in the change of the contact angle when switching from the E to the Z isomer. Indeed, the change in contact angle increased from only 7^∘ for homogeneous monolayers to about 20^∘ for nanostructured surfaces using AAP aggregates.

Keywords: Wetting; Photoswitches; Interfaces and Surfaces