Molecular Insights into the Interfacial Adhesion and Chain Adsorption of Silicone Polymers via Nanoindentation

Z Wu and MN Salimi and DC Webster and AB Croll and WJ Xia, MACROMOLECULES, 58, 9763-9775 (2025).

DOI: 10.1021/acs.macromol.5c01840

Silicone-based polymers, particularly polydimethylsiloxane (PDMS), are esteemed for their exceptional thermal stability, hydrophobicity, and biocompatibility. This study leverages atomistically informed coarse- grained molecular dynamics (CG-MD) simulations to explore the interfacial adhesive characteristics of PDMS films subjected to nanoindentation, with a focus on the influences of interfacial interaction strength between nanoindenter and polymer chains, temperature, and cross-link density, interpreted through the classic Johnson-Kendall-Roberts (JKR) model. Our findings reveal that increasing the interfacial interaction strength significantly enhances adhesion, necessitating a greater energy for separation. Notably, beyond a certain threshold, the adhesion exhibits a plateau, as quantified by the apparent critical energy release rate, G c. This saturation in G c can be attributed to chain adsorption on the indenter tip. Such an interfacial adsorption phenomenon becomes more pronounced at elevated temperatures along with a concomitant decrease in G c, due to enhanced chain mobility. Additionally, increasing cross-link density of the PDMS network reduces chain adsorption during indentation, thereby resulting in a higher apparent G c. Our simulation results, confirmed by the experimental Atomic Force Microscopy (AFM) measurements, offer valuable insights into interfacial behavior of silicone-based polymers, highlighting the intricate interplay among interaction strength, temperature, and cross-link density in quantifying adhesive properties of PDMS films.

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