Molecular dynamics simulations for interfacial structure and affinity between carboxylic acid-modified Al2O3 and...

Area of Science:

• Materials Science
• Computational Chemistry
• Polymer Science

Background:

• Controlling nanoparticle dispersion in polymer matrices is essential for creating advanced polymer nanocomposites.
• Surface modification of nanoparticles is a key strategy to improve their compatibility and dispersion within polymers.
• Molecular dynamics (MD) simulations offer valuable insights into interfacial properties, aiding material design.

Purpose of the Study:

• To investigate the impact of surface coverage, modifier length, and polymer type on the interfacial properties of surface-modified Al2O3 nanoparticles in polymer melts.
• To quantify the interfacial affinity using the work of adhesion (Wadh) and work of immersion (Wimm).
• To establish relationships between interfacial properties and polymer-modifier interactions.

Main Methods:

• Utilized all-atom molecular dynamics (MD) simulations to model nanoparticle-polymer interfaces.
• Employed surface modifiers: hexanoic, decanoic, and tetradecanoic acids.
• Investigated polymer melts: polypropylene (PP), polystyrene (PS), and poly(methyl methacrylate) (PMMA).
• Calculated Wadh via the phantom-wall approach and Wimm derived from Wadh and polymer surface tension.

Main Results:

• Surface modification, particularly at low coverage, significantly enhanced both Wadh and Wimm due to improved polymer penetration.
• Modifier length exhibited a minor influence on interfacial affinity.
• Work of adhesion (Wadh) followed the trend PP < PS < PMMA, while work of immersion (Wimm) showed the opposite trend: PMMA < PS < PP.
• Interfacial affinity trends were successfully correlated with the Flory-Huggins interaction parameter (χ).

Conclusions:

• Interfacial affinity in polymer nanocomposites can be effectively tuned by adjusting nanoparticle surface coverage and modifier selection.
• The choice of surface modifier and its interaction with the specific polymer matrix are critical for optimizing nanocomposite performance.
• MD simulations provide a powerful tool for predicting and guiding the design of materials with desired interfacial properties.