Dynamic Heterogeneity of Filler-Associated Interphases in Polymer Nanocomposites

Area of Science:

• Polymer Science
• Materials Science
• Nanotechnology

Background:

• Dynamically inhomogeneous polymer systems feature interphases with mobility gradients, crucial for material performance.
• Particle-filled rubber, a polymer nanocomposite, can exhibit immobilized layers around fillers due to favorable interactions.
• Intermediate mobility regions may form distinct layers or dispersed dynamic heterogeneities.

Purpose of the Study:

• To investigate the nanoscale structure of mobility gradients in silica-filled acrylate rubber.
• To differentiate between shell-like layers and dynamic heterogeneities in polymer nanocomposites.
• To provide microscopic insights into polymer dynamics near filler interfaces.

Main Methods:

• Bidirectional proton NMR spin diffusion (SD) experiments.
• Numerical simulations of polymer dynamics.
• Analysis of experimental data across varying spin diffusion mixing times.

Main Results:

• Short-time NMR spin diffusion data strongly support the presence of dynamic heterogeneities.
• Model calculations for different structural scenarios fit longer mixing time data similarly well.
• Distinguishing between distinct layers and dispersed subdomains requires short-time dynamics analysis.

Conclusions:

• The study concludes that dynamic heterogeneities, rather than distinct shell-like layers, are present in the investigated polymer nanocomposite.
• The findings highlight the importance of short-time dynamics in characterizing nanoscale mobility in polymers.
• Proton NMR spin diffusion combined with simulations offers a powerful approach to understanding polymer interphases.