Size effects on rotational particle diffusion in complex fluids as probed by Magnetic Particle Nanorheology
| Autor: | Markus Zylla, Melissa Hess, Heiko Wende, Samira Webers, Annette M. Schmidt, Patricia Rochels, Eric Roeben |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Length scale
Materials science Hydrodynamic radius General Physics and Astronomy 02 engineering and technology Magnetic particle inspection Physik (inkl. Astronomie) 010402 general chemistry 021001 nanoscience & nanotechnology Thermal diffusivity 01 natural sciences 0104 chemical sciences Chemical physics ddc:540 Radius of gyration Particle Particle size Physical and Theoretical Chemistry 0210 nano-technology Complex fluid |
| Zdroj: | Physical chemistry, chemical physics 21(48), 26525-26539 (2019). doi:10.1039/C9CP04083H |
| DOI: | 10.1039/C9CP04083H |
| Popis: | Rheological approaches based on micro- or nanoscopic probe objects are of interest due to the low volume requirement, the option of spatially resolved probing, and the minimal-invasive nature often connected to such probes. For the study of microstructured systems or biological environments, such methods show potential for investigating the local, size-dependent diffusivity and particle–matrix interactions. For the latter, the relative length scale of the used probes compared to the size of the structural units of the matrix becomes relevant. In this study, a rotational-dynamic approach based on Magnetic Particle Nanorheology (MPN) is used to extract size- and frequency-dependent nanorheological properties by using an otherwise well-established polymer model system. We use magnetically blocked CoFe2O4 nanoparticles as tracers and systematically vary their hydrodynamic size by coating them with a silica shell. On the polymer side, we employ aqueous solutions of poly(ethylene glycol) (PEG) by varying molar mass M and volume fraction ϕ. The complex Brownian relaxation behavior of the tracer particles in solutions of systematically varied composition is investigated by means of AC susceptometry (ACS), and the results provide access to frequency dependent rheological properties. The size-dependent particle diffusivity is evaluated based on theoretical descriptions and macroscopic measurements. The results allow the classification of the investigated compositions into three regimes, taking into account the probe particle size and the length scales of the polymer solution. While a fuzzy cross-over is indicated between the well-known macroscopic behavior and structurally dominated spectra, where the hydrodynamic radius is equal to the radius of gyration of the polymer (rh ∼ Rg), the frequency-related scaling behavior is dominated by the correlation length ξ respectively by the tube diameter a in entangled solutions for rh < Rg. |
| Databáze: | OpenAIRE |
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