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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 20: General Session to the Symposium: Interplay of Substrate Adaptivity and Wetting Dynamics from Soft Matter to Biology (joint session CPP/DY)

CPP 20.2: Vortrag

Mittwoch, 7. September 2022, 09:45–10:00, H39

Memory effects of PNiPAAm brushes in different atmospheres — •Simon Schubotz, Marisa Fischer, Jens-Uwe Sommer, Petra Uhlmann, Andreas Fery, and Günter Auernhammer — Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany

Some polymer brushes show a co-nonsolvency effect: They collapse in a mixture of two good solvents at some specific mixing ratio. In contrast to previous studies we concentrate on partial wetting of co-nonsolvent polymer brushes, i.e., on the dynamics of a three-phase contact line moving over such brushes.

We found that Poly(N-isopropylacrylamide) (PNiPAAm) brushes experiences a memory effect when consecutively depositing drops at the same position. Previously deposited drops adapt the brush and changes the wetting behavior (advancing contact angle) of subsequent drops.

We measure water drops in an ethanol-saturated atmosphere on PNiPAAm brushes. The measurements show that the memory effect is strongly effected by an ethanol-enriched atmosphere. At the three-phase contact line, due to evaporation from the drop, the composition of the atmosphere and probably also the brush will transition from an ethanol-rich state to a water-enriched state. Thus, the brush might pass through the co-nonsolvency regime. On large time scales the ethanol enriched gas phase and the water drop will become mixtures of ethanol and water. We present strategies to counter this mixing effect.