# In Situ Microscopy of 2‑Dimensional Carbon Nanotube Liquid Crystals at Liquid/Liquid Interfaces

## TL;DR

Researchers used microscopy to study how carbon nanotubes self-organize at liquid interfaces, which could help create better electronic circuits.

## Contribution

The study reveals how carbon nanotubes form liquid crystalline phases at liquid interfaces and how additives influence their ordering.

## Key findings

- CNTs spontaneously form liquid crystalline phases at liquid interfaces, with density depending on CNT concentration.
- LC domains are polycrystalline, with domain size influenced by LC formation kinetics.
- Additives can alter interfacial dynamics, affecting domain characteristics through Marangoni flow or CNT transport.

## Abstract

Carbon nanotubes (CNTs) must be ordered into densely
aligned arrays
to fully exploit their electronic properties in next-generation integrated
circuits. Recent advances have shown that CNTs can accumulate and
self-order at liquid–liquid interfaces, from which the CNTs
can be transferred onto a substrate to create dense CNT arrays with
remarkable electronic characteristics. Here, by leveraging in situ polarized optical microscopy, we investigate the
self-assembly of CNTs at organic solvent–water interfaces and
answer key questions about CNT assembly structure and formation kinetics.
We find that CNTs spontaneously form liquid crystalline (LC) phases
at the liquid–liquid interface with a density strongly dependent
on the concentration of CNTs in the organic solvent ink. This LC behavior
is robust across a range of polymer wrappers, including polyfluorenes,
triblock copolymers, and polycarbazole (PCz). Polarized microscopy
reveals that the resulting LC domains are polycrystalline in nature
with domain size governed by the kinetics of LC formation. Additives
can alter interfacial dynamicseither by promoting Marangoni
flow or by enhancing CNT transportoffering an avenue to tune
domain characteristics. We find that the LC domain structure formed
at the interface is largely preserved upon transfer to a solid substrate,
indicating that optimizing interfacial ordering is key to achieving
high-quality CNT arrays for electronic applications. In cases where
distortions occur during transfer, they often arise from a mismatch
between the substrate translation speed and the transport velocity
of the LC to the solid surface.