Regensburg 2022 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 37: Interfaces and Thin Films and Responsive and Adaptive Systems

CPP 37.2: Vortrag

Donnerstag, 8. September 2022, 11:00–11:15, H39

Water Induced Polymer Reorientation at a Polystyrene/ Polyacrylic Acid Surface — Xiaomei Li¹, Mirela Encheva², Kaloian Koynov¹, Hans-Jürgen Butt¹, Ellen Backus², and •Rüdiger Berger¹ — ¹Max Planck Institute for Polymer Research, 55128 Mainz, Germany — ²University of Vienna, Währinger Straße 42, 1090 Vienna, Austria

Polymers are capable of undergoing adaptation phenomena triggered by exposure to liquids. Here we study the adaptation of copolymer films formed by polystyrene and polyacrylic acid (PS/PAA) after water exposure. We measured the dynamic advancing and receding contact angles (CA) of water drops sliding down a PS/PAA film. We associate the gradual increase in advancing CA with drop velocity to the adaptation process to water. By applying adaptation theory, we estimated the time constant of this adaptation process to be much smaller than 1 s. The changes in contact angles may be caused by swelling of the copolymer and/or by a reorientation of the hydrophilic segments (PAA) towards the surface. Therefore, we performed vibrational sum frequency generation (SFG) spectroscopy which is surface sensitive. SFG experiments before and after exposing the copolymer to water reveal a decrease in intensity of the vibrational band representing the PS segments, suggesting a reorientation of the polymer groups at the surface upon contact with water.