Evolution of Fragments Formed at the Rupture of a Knotted Alkane Molecule

TL;DR

This study uses first-principles molecular dynamics to investigate the early-stage chemical evolution of radicals formed after rupture of a knotted alkane molecule, revealing recombination, cyclic formation, and disproportionation phenomena.

Contribution

It provides new insights into the ultrafast chemical processes occurring immediately after polymer chain rupture at the molecular level.

Findings

Radicals can recombine or form cyclic alkanes.

Disproportionation phenomena occur with nearby chain segments.

Ultrafast spectroscopy can potentially observe these phenomena.

Abstract

Common experience tells us that a knot significantly weakens the polymer strand in which it is tied, which in turn leads to more facile chain rupture under tensile loading. Using first-principles molecular dynamics calculations we describe the dynamical evolution of the radicals that form after chain rupture of a single knotted alkane molecule in their very early stages of life. They are able to recombine, to form cyclic alkanes and to undergo disproportionation phenomena with nearby chain segments. The breaking of a single knotted polymer chain under mechanical loading is thus predicted to reveal phenomena falling in the domain of ultrafast spectroscopy.