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Engineering interfacial entropic effects to generate giant viscosity changes in nanoparticle embedded polymer thin
Aparna Swain1, Nafisa Begam1, Sivasurender Chandran2
1Department of Physics, Indian Institute of Science, Bangalore 560012, India. basu@iisc.ac.in.
Soft Matter
|April 15, 2020
Summary
This study introduces a new atomic force microscopy method to measure the viscosity of polymer nanocomposite (PNC) thin films. The research reveals that interfacial interactions can dramatically alter PNC film viscosity, suggesting a new theoretical model is needed.
Area of Science:
- Materials Science
- Polymer Science
- Nanotechnology
Background:
- Thin polymer and polymer nanocomposite (PNC) films are crucial functional coatings.
- Film properties, especially thermo-mechanical behavior, differ from bulk materials.
- Measuring transport properties like viscosity in thin films is challenging due to limited techniques.
Purpose of the Study:
- To develop and demonstrate a novel method for measuring the viscosity of PNC thin films.
- To investigate the influence of polymer-grafted nanoparticle (PGNP) characteristics on film viscosity.
- To explore the relationship between interfacial interactions and viscosity in PNC films.
Main Methods:
- Utilized atomic force microscopy (AFM) based force-distance spectroscopy to measure viscosity.
- Investigated PNC thin films with PGNP dispersed in homopolymer melts.
- Systematically tuned the PGNP-polymer interfacial entropic interaction parameter (f) via molecular weight ratios.
Main Results:
- Observed significant viscosity reduction at low f and giant enhancement at high f.
- The observed viscosity changes were more pronounced with increasing PGNP loading (φ).
- Existing theoretical models failed to explain the experimental viscosity variations.
Conclusions:
- Demonstrated the tunability of interfacial entropic effects to control PNC coating viscosity.
- Highlighted the potential utility of these findings in various material applications.
- Indicated a new viscosity variation regime in athermal PNC films, necessitating new theoretical frameworks.
