Regensburg 2025 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: Interfaces and Thin Films I
CPP 20.5: Talk
Tuesday, March 18, 2025, 12:45–13:00, H38
Thermo-Responsive Surface Structure and Wetting of Polymer Brushes with Octadecyl Side Chains — •Billura Shakhayeva1, Franziska Neuhaus1, Luciana Buonaiuto2, Sander Reuvekamp2, Sissi de Beer2, Frieder Mugele2, and Björn Braunschweig1 — 1University of Münster, Institute of Physical Chemistry, Münster (Germany) — 2University of Twente, Physics of Complex Fluids, Enschede (The Netherlands)
Polymers are extensively studied as coatings due to their ability to respond to environmental changes, such as temperature or humidity variations, which greatly influence their wettability. This study investigates the effect of temperature on the molecular structure of poly-octadecylmethylacrylate (P18MA) brushes and their wetting behavior with hexadecane. Vibrational sum-frequency generation (SFG) spectroscopy was used to examine the molecular structure at the brush surface, both in air and in contact with hexadecane, by recording in situ SFG spectra near the three-phase contact line. The SFG spectra showed strong CH stretching bands of the octadecyl side chains at the air interface, indicating partial chain ordering that varies with temperature. For brushes in air, a phase transition at 311 K was identified as the surface melting temperature, 3 K higher than the bulk melting point. In the presence of hexadecane, surface melting occurred at 309 K, likely due to liquid penetration. Optical microscopy also revealed halo formation around the drop, suggesting local brush swelling. Below the surface melting point, the contact angle gradually decreased, while crossing the melting point enhanced hexadecane spreading.
Keywords: Polymer brushes; Surface melting; Wetting