Microstructure of amide-functionalized polyethylenes determined by NMR relaxometry

TL;DR

This paper uses NMR to study how adding amide groups affects the structure of polyethylene materials.

Contribution

The study reveals that amidyl groups partition into the rigid amorphous fraction of polyethylenes, altering their microstructure.

Findings

Amide functionalization reduces crystallinity in polyethylenes.

Amidyl groups localize in the rigid amorphous fraction between crystalline and amorphous regions.

NMR relaxation techniques provide precise insights into polymer microstructure.

Abstract

Amidation of polyethylenes creates a range of amide-containing materials with enhanced properties, but the effect of these functional groups on the microstructure of these new materials is not known. Here we employ solid-state nuclear magnetic resonance (NMR) techniques to analyze the microstructure of amide-modified polyethylenes. While a decrease in crystallinity was observed with increasing amounts of functionalization, we found by measuring the chain mobility of the crystalline, amorphous, and interphasial regions of the polyethylenes with NMR relaxation techniques that the grafted amidyl groups partition into the rigid amorphous fraction (RAF) between the crystalline and amorphous regions. The chemical specificity of these NMR experiments creates precise assessments of the location of functional groups within the materials. Together, these insights into the microstructure and morphology of amide-containing polyethylenes lay a foundation for a deeper understanding of the structure and properties of functional polyolefins.

NMR relaxation studies reveal that pendant amidyl groups on polyethylenes alter microstructure and chain dynamics. These groups are localized in the rigid amorphous fraction of the polymers and lead to changes in bulk properties.

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