Dynamics of ultra-thin polystyrene with and without a (artificial) dead layer studied by resonance enhanced dynamic light scattering
| Autor: | Hatice Duran, Markus A. Plum, Fan-Yen Lin, Werner Steffen, Sulivan Dias Borges Vianna |
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| Rok vydání: | 2017 |
| Předmět: |
Capillary wave
Special Topic: Dynamics of Polymer Materials in Thin Films and Related Geometries Materials science General Physics and Astronomy 02 engineering and technology 01 natural sciences Viscoelasticity Physics::Fluid Dynamics Condensed Matter::Materials Science chemistry.chemical_compound Viscosity Optics Dynamic light scattering Condensed Matter::Superconductivity 0103 physical sciences Physical and Theoretical Chemistry Composite material Thin film 010306 general physics chemistry.chemical_classification business.industry Relaxation (NMR) Polymer 021001 nanoscience & nanotechnology Condensed Matter::Soft Condensed Matter chemistry Polystyrene 0210 nano-technology business |
| Zdroj: | The Journal of Chemical Physics. 146:203333 |
| ISSN: | 1089-7690 0021-9606 |
| Popis: | Using non-invasive, marker-free resonance enhanced dynamic light scattering, the dynamics of capillary waves on ultrathin polystyrene films’ coupling to the viscoelastic and mechanical properties have been studied. The dynamics of ultrathin polymer films is still debated. In particular the question of what influence either the solid substrate and/or the fluid-gas interface has on the dynamics and the mechanical properties of films of glass forming liquids as polymers is in the focus of the present research. As a consequence, e.g., viscosity close to interfaces and thus the average viscosity of very thin films are prone to change. This study is focused on atactic, non-entangled polystyrene thin films on the gold surface. A slow dynamic mode was observed with Vogel-Fulcher-Tammann temperature dependence, slowing down with decreasing film thickness. We tentatively attribute this relaxation mode to overdamped capillary waves because of its temperature dependence and the dispersion with a wave vector which was found. No signs of a more mobile layer at the air/polymer interface or of a “dead layer” at the solid/polymer interface were found. Therefore we investigated the influence of an artificially created dead layer on the capillary wave dynamics by introducing covalently bound polystyrene polymer brushes as anchors. The dynamics was slowed down to a degree more than expected from theoretical work on the increase of density close to the solid liquid interface—instead of a “dead layer” of 2 nm, the interaction seems to extend more than 10 nm into the polymer. |
| Databáze: | OpenAIRE |
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