Grafted Nanoparticle Surface Wetting during Phase Separation in Polymer Nanocomposite Films.

Area of Science:

• Materials Science
• Polymer Science
• Nanotechnology

Background:

• Wetting in polymer nanocomposites (PNCs) is governed by surface energy differences and bulk thermodynamics (interaction parameter, χ).
• Understanding nanoparticle behavior in PNCs is crucial for tailoring material properties.

Purpose of the Study:

• To investigate the interplay of wetting and phase separation in PNCs.
• To analyze the behavior of polymethyl methacrylate (PMMA)-grafted silica nanoparticles (NPs) in a poly(styrene-ran-acrylonitrile) (SAN) matrix.
• To explore the influence of annealing temperature and quench depth on NP distribution and wetting.

Main Methods:

• Atomic force microscopy (AFM) to study particle areal density.
• Transmission electron microscopy (TEM) for imaging NP wetting and column formation.
• Grazing-incidence Rutherford backscattering spectrometry (GI-RBS) to quantify surface excess (Z*).

Main Results:

• PMMA-NPs increased areal density, approaching random close packing, and prevented dewetting.
• NPs formed columns spanning the free surface and substrate interface, with higher density at 190 °C.
• Surface excess (Z*) increased with time and quench depth, indicating unfavorable PMMA-SAN interactions.

Conclusions:

• PMMA-NPs effectively control wetting and phase separation in PNCs.
• Observed diffusion coefficients for PMMA-NPs were higher than theoretical predictions.
• Findings are valuable for nanotechnology applications requiring control over surface properties like wettability and durability.