Thermophoresis of a Colloidal Rod: Contributions of Charge and Grafted Polymers
| Autor: | Simone Wiegand, Jan K. G. Dhont, Zilin Wang, Yi Liu, Peter R. Lang, Doreen Niether, Johan Buitenhuis |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Materials science
Model system 02 engineering and technology 010402 general chemistry 01 natural sciences Thermophoresis Colloid symbols.namesake Electrochemistry General Materials Science Spectroscopy Debye length chemistry.chemical_classification Quantitative Biology::Biomolecules Charge (physics) Surfaces and Interfaces Polymer 021001 nanoscience & nanotechnology Condensed Matter Physics 0104 chemical sciences Condensed Matter::Soft Condensed Matter chemistry Chemical physics Ionic strength ddc:540 symbols 0210 nano-technology |
| Zdroj: | Langmuir 35(4), 1000-1007 (2019). doi:10.1021/acs.langmuir.8b03614 |
| ISSN: | 1520-5827 |
| Popis: | In this study we investigated the thermodiffusion behavior of a colloidal model system as function of Debye length, $\lambda_{\mathrm {DH}}$, which is controlled by the ionic strength. Our system consists of an fd-virus grafted with polyethylene glycol (PEG) with a molecular mass of 5000 g/mol. The results are compared with recent measurements on bare \textit{fd}-virus and results of PEG. The diffusion coefficients of both viruses are comparable and increase with increasing Debye length. The thermal diffusion coefficient, $D_{\mathrm T}$, of the bare virus increases strongly with the Debye length, while $D_{\mathrm T}$ of the grafted fd-virus shows only a very weak increase. The Debye length dependence of both systems can be described with an expression derived for charged rods using the surface charge density and an offset of $D_{\mathrm T}$ as adjustable parameters. It turns out that the ratio of the determined surface charges is inverse to the ratio of the surfaces of the two systems, which means that the total charge remains almost constant. The determined offset of the grafted fd-virus describing the chemical contributions is the sum of $D_{\mathrm T}$ of PEG and the offset of the bare \textit{fd}-virus. At high $\lambda_{\mathrm DH}$, corresponding to low ionic strength, the $S_{\mathrm T}$-values of both colloidal model systems approach each other. This implies a contribution from the polymer layer, which is strong at short $\lambda_{\mathrm DH}$ and fades out for the longer Debye lengths, when the electric double layer reaches further than the polymer chains and therefore dominates interactions with the surrounding water. |
| Databáze: | OpenAIRE |
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