Adhesion and Separation of Nanoparticles on Polymer-Grafted Porous Substrates

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Nanoparticle-polymer brush interactions are crucial for applications like chromatographic separation.
• Understanding these interactions is key to controlling nanoparticle behavior in confined environments.

Purpose of the Study:

• To investigate the free energy landscapes and transport of functionalized nanoparticles (NPs) within polymer brush (PB)-grafted channels.
• To analyze how solvent composition influences NP-PB interactions and chromatographic separation.
• To explore the potential for size-independent nanoparticle separation based on surface chemistry.

Main Methods:

• Dissipative particle dynamics (DPD) simulations were employed to model NP-PB systems.
• Ghost tweezers free energy calculations were used to determine energy landscapes.
• Analysis of NP transport, mean velocity, and retention time under varying solvent conditions.

Main Results:

• NP-PB adhesion is governed by polymer adsorption and entropic repulsion, both sensitive to solvent composition.
• A transition in NP separation was observed: from size exclusion (larger NPs elute faster) to adsorption (smaller NPs elute faster) as poor solvent fraction increases.
• A critical regime analogous to polymer chromatography was identified, where NP retention time becomes independent of size.

Conclusions:

• Solvent composition can tune the separation mechanism of nanoparticles in polymer brush-grafted channels.
• The findings suggest the possibility of nanoparticle chromatography based on surface chemistry rather than size.
• This offers a novel approach for separating nanoparticles with similar surface properties regardless of their size.