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Towards Polymers with Molecular Auxeticity.

Mahshid Alizadeh, Iris K Tennie, Ullrich Steiner

|March 1, 2019

Summary

This summary is machine-generated.

Researchers designed a novel aromatic macrocycle to create molecular-level auxetic materials. This material expands perpendicularly when stretched, mimicking re-entrant structures, by undergoing cis-trans amide isomerization under tensile force.

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Area of Science:

Materials Science
Supramolecular Chemistry
Polymer Chemistry

Background:

Auxetic materials exhibit counterintuitive negative Poisson's ratio, expanding perpendicularly to applied tensile force.
Synthesizing auxetic behavior at the molecular level has been a long-standing challenge in materials science.
Existing auxetic materials often rely on complex macromolecular architectures.

Purpose of the Study:

To design and synthesize a molecular-level auxetic material using an aromatic macrocycle.
To investigate the mechanism of auxetic behavior through controlled cis-trans isomerization.
To demonstrate the feasibility of creating auxetic properties in synthetic molecules.

Main Methods:

Design of an aromatic macrocycle with a sequence of N-substituted and N-unsubstituted amides.
Incorporation of a cis-trans aramide motif into an end-functionalized polymer for AFM attachment.
Utilizing atomic force microscopy (AFM) to apply tensile force and observe configurational changes.

Main Results:

A novel aromatic macrocycle was designed to mimic re-entrant structures of macromolecular auxetics.
The molecule was engineered to undergo cis-trans amide isomerization upon tensile force application.
AFM experiments were conducted on a polymer-tethered system to probe the molecular response.

Conclusions:

The designed aromatic macrocycle shows potential for achieving molecular-level auxetic behavior.
The cis-trans isomerization mechanism provides a pathway for perpendicular expansion under tension.
This study opens new avenues for designing advanced functional materials with tunable mechanical properties.