Diffusion of Nanoparticles with Activated Hopping in Crowded Polymer Solutions

Area of Science:

• Soft Matter Physics
• Polymer Science
• Nanotechnology

Background:

• Long-distance diffusion of nanoparticles (NPs) in crowded environments is considered improbable.
• The mechanisms governing NP movement in such complex media are not well understood.

Purpose of the Study:

• To experimentally investigate the occurrence and characteristics of long-distance nanoparticle hops in crowded environments.
• To elucidate the underlying mechanisms of NP diffusion in entangled polymer solutions.

Main Methods:

• Experimental observation of large NPs in crowded entangled poly(ethylene oxide) (PEO) solutions.
• Analysis of NP diffusion as a superposition of activated hopping and polymer reptation.
• Characterization of time-dependent non-Gaussianity in NP diffusion.

Main Results:

• Identified intermittent, long-distance hops of large NPs in crowded PEO solutions, attributed to thermally induced activated hopping.
• Demonstrated that NP diffusion is a combination of activated hopping and polymer reptation.
• Showed that activated hopping is significant with high PEO molecular weight or small NP size.
• Revealed NP diffusion's non-Gaussianity arises from competition between polymer relaxation, hopping, and reptation.
• Proposed an exponential scaling law for hopping time, linking energy barrier to NP size.

Conclusions:

• Activated hopping is a key mechanism for long-distance NP transport in crowded polymer solutions.
• NP motion is governed by a balance between local polymer dynamics and NP size.
• Findings offer crucial insights for nanomedicine delivery and targeting in biological settings.