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Dynamics of Nanoparticles in Entangled Polymer Solutions
Pooja Nath, Rahul Mangal1, Ferdinand Kohle
1Department of Chemical Engineering, Indian Institute of Technology Kanpur , Kanpur, Uttar Pradesh 208016, India.
Langmuir : the ACS Journal of Surfaces and Colloids
|December 2, 2017
Summary
Nanoparticle probes move faster than predicted in polymer solutions, interacting with local fluid segments rather than the bulk. This localized drag effect deviates significantly from continuum predictions, especially for smaller nanoparticles.
Area of Science:
- Soft Matter Physics
- Polymer Science
- Nanotechnology
Background:
- Understanding nanoparticle dynamics in complex fluids like polymer solutions is crucial for various applications.
- Existing models often assume continuum hydrodynamics, which may not apply at the nanoscale.
Purpose of the Study:
- To investigate the mean square displacement (MSD) of nanoparticle probes in polymer solutions.
- To explore how nanoparticle size relative to polymer length scales influences their dynamics.
- To elucidate the origins of anomalous drag forces experienced by nanoparticles.
Main Methods:
- Fluorescence Correlation Spectroscopy (FCS)
- Single-Particle Tracking (SPT)
- Analysis using the Cai et al. hopping model
Main Results:
- In polymer solutions, nanoparticles smaller than the radius of gyration (Rg) exhibit faster dynamics than predicted by continuum models.
- Nanoparticles interact hydrodynamically with local fluid segments, experiencing effective drag comparable to polymer chain segments.
- When nanoparticle diameter exceeds entanglement mesh size (a), dynamics transition from diffusive to subdiffusive.
Conclusions:
- Polymer molecules exert non-continuum resistance, leading to localized drag on nanoparticles.
- The Stokes-Einstein relation is insufficient for predicting nanoparticle dynamics in polymer solutions under certain conditions.
- The hopping model provides a framework for understanding nanoparticle transport and local drag in entangled polymer solutions.
