Interpreting Aqueous Two-Phase Extraction of Single-Walled Carbon Nanotubes with Highly Versatile Nonionic Polymers

TL;DR

This paper explores how nonionic polymers, especially PEPEG, can be used in aqueous two-phase extraction to selectively isolate single-walled carbon nanotubes based on chirality, providing new mechanistic insights.

Contribution

It introduces the use of polyethylene-block-poly(ethylene glycol) in ATPE, revealing its versatility and chirality-sensitive partitioning for SWCNT purification.

Findings

PEPEG can form biphasic systems and act as a phase-forming component.

PEPEG exhibits chirality-sensitive preference toward SWCNTs.

Extraction conditions can be tailored to enrich specific SWCNT chiralities.

Abstract

The development of efficient separation methods is essential for the production of fine chemicals and materials. Among them, the aqueous two-phase extraction (ATPE) allows for the isolation of single-walled carbon nanotubes (SWCNTs) of specific structures and other substances. However, this easy-to-use method, in which an analyte is partitioned between two phases, still demands a better understanding of its mechanism to make its application more effective. Herein, we demonstrate how various biphasic systems can be formed according to the nature of the phase-forming components. Moreover, by employing polyethylene-block-poly(ethylene glycol) (PEPEG), previously unrecognized in this context, we reveal the versatility of nonionic polymers for ATPE, which can successfully act as phase-forming compounds, partitioning modulators, and dispersing agents. Interestingly, as proven by experiments and modelling, PEPEG exhibited chirality-sensitive preference toward SWCNTs, which can significantly facilitate the purification of SWCNTs using various approaches. Capitalizing on this finding, we report how the extraction environment may be tailored to promote the isolation of (8,3) SWCNTs and other chirality-enriched SWCNT fractions. The relationships noted, based on the examination of a model material (SWCNTs), provide substantial insight into the elusive mechanism of the ATPE purification approach, widely employed across a range of analytes, from cell organelles to nanostructures