Influence of polymer flexibility on nanoparticle dynamics in semidilute solutions

Area of Science:

• Polymer Physics
• Soft Matter Physics
• Computational Biophysics

Background:

• Nanoparticle (NP) transport in polymer solutions is governed by the solution's hierarchical structure and dynamics.
• Understanding this transport is crucial for various applications, including drug delivery and materials science.

Purpose of the Study:

• To investigate the effect of polymer chain stiffness on nanoparticle transport dynamics.
• To compare simulation results with established theoretical models like Stokes-Einstein relation (SER), mode-coupling theory (MCT), and polymer coupling theory (PCT).

Main Methods:

• Multi-particle collision dynamics (MPCD) simulations were employed.
• Simulations focused on semiflexible polymer chains with tunable persistence length (lp).
• Nanoparticle diffusion coefficients and dynamics were analyzed across different time scales.

Main Results:

• Nanoparticles exhibited two regimes: subdiffusion at short times and diffusion at long times.
• Increasing polymer stiffness (lp) led to deviations from SER and PCT, indicating NP motion decoupling from bulk viscosity.
• Long-time NP diffusion was accurately described by MCT, especially at high polymer concentrations.
• Short-time subdiffusion dynamics were strongly dependent on polymer flexibility, becoming more pronounced with increased stiffness.

Conclusions:

• Polymer chain stiffness is a critical factor influencing NP transport, leading to behaviors not fully captured by theories for flexible chains.
• MCT provides a robust framework for describing long-time NP diffusion in semiflexible polymer solutions.
• Differences in segmental mobility of semiflexible chains likely explain the observed NP dynamics and their decoupling from polymer motion.