Probing Viscoelastic Properties and Interfaces in High-Density Polyethylene Vitrimers at the Nanoscale Using Dynamic...

Area of Science:

• Polymer Science and Engineering
• Materials Science and Nanotechnology

Background:

• Vitrimers offer a unique combination of thermoset and thermoplastic properties.
• Understanding the nanoscale structure and interfaces in vitrimers is crucial but challenging.
• Dynamic cross-linking significantly influences vitrimer viscoelastic behavior.

Purpose of the Study:

• To characterize the nanoscale viscoelastic properties and interfaces in high-density polyethylene (HDPE) vitrimers.
• To investigate the correlation between vitrimer nanostructure and bulk material behavior.

Main Methods:

• Utilized dynamic modes of atomic force microscopy (AFM), including intermodulation AFM (ImAFM) and AFM-based dynamic mechanical analysis (AFM-nDMA).
• Employed k-means clustering algorithm for phase analysis.
• Quantified local viscoelastic properties and adhesion forces at the nanoscale.

Main Results:

• Identified two distinct phases with differing viscoelastic properties in the HDPE vitrimer system.
• Revealed a cross-linking-rich network structure within a cross-linking-poor matrix at the nanoscale.
• Observed higher adhesion forces in the cross-linking-rich regions compared to the matrix.

Conclusions:

• The nanoscale heterogeneity and viscoelastic properties of HDPE vitrimers are elucidated.
• Findings provide explanations for enhanced bulk properties such as decreased crystallinity and increased dimensional stability.
• This research offers critical insights into the structure-property relationships governing vitrimer behavior.