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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 1: Focus: Morphology of Complex Polymer Mesophases: From Experiment to Modelling - organized by Kostas Daoulas and Volker Abetz

CPP 1.2: Hauptvortrag

Montag, 1. April 2019, 10:00–10:30, H14

Gradient dynamics models for films of complex fluids and beyond - Dewetting, line deposition and crystallisation — •Uwe Thiele — Institut für Theoretische Physik and Center for Nonlinear Science, Universität Münster.

First, we review situations where the dynamics of phase transitions creates structures, e.g., dewetting polymer mixtures, Langmuir-Blodgett (LB) transfer of surfactants or colloidal crystallisation. After presenting typical hydrodynamic thin-film models we rewrite them as gradient dynamics on some energy functional that accounts for wettability and capillarity. This allows for many consistent extensions, e.g., towards solute-dependent wettability. As example we show that a film of a mixture may become unstable through coupled film height and concentration fluctuations. Next, we consider gradient dynamics models for films covered by surfactants. Such models may be employed to describe the formation of line patterns during LB transfer of a surfactant layer from a bath onto a moving plate. After showing simulations with the full model, we sketch how line deposition is reflected in an intricate bifurcation structure that one can analyse within a Cahn-Hilliard-type model. Finally, we consider colloidal crystallisation employing gradient dynamics models, namely, dynamical density functional theory (DDFT) and its local approximation, the phase field crystal (PFC) model. We analyse crystallisation fronts and show that their speeds may be obtained via a marginal stability criterion and relate it to created disorder and subsequent aging. Finally, we discuss the relation of localised states and an amorphous solid phase.