# Controlled adsorption of polyurethane onto chlorine-modified carbon nanotubes for enhanced mechanical and electrical properties of nanocomposites

## TL;DR

This paper introduces a method to improve the mechanical and electrical properties of nanocomposites by controlling how polyurethane adsorbs onto modified carbon nanotubes.

## Contribution

A one-step filtration method with solubility modulation is used to control polyurethane adsorption on chlorine-modified carbon nanotubes, enhancing nanocomposite properties.

## Key findings

- Chlorine modification improves electrical conductivity and interfacial interactions in SWCNT–TPU nanocomposites.
- Adsorption isotherms reveal mechanisms behind interfacial interactions and guide optimization of composite properties.
- Optimal SWCNT/TPU ratios and processing conditions significantly enhance mechanical and electrical performance without reducing strain.

## Abstract

Maximizing the performance of carbon nanotubes (CNTs) in polymer nanocomposites remains a significant challenge, and fabrication methods often fall short of achieving the desired properties. From an application perspective, enhancing both mechanical properties and electrical conductivity is particularly desirable, yet simultaneously improving multiple properties is often difficult – the high loadings in dispersed CNT composites needed for better conductivity tend to impede processing and mechanical properties. Herein, a one-step filtration method with solubility modulation to control the adsorption of thermoplastic polyurethane (TPU) onto a commercial-grade single-wall CNT (SWCNT) powder is employed. The impact of solvent choice on interfacial interactions, the properties and microstructure of SWCNT–TPU nanocomposite sheets is highlighted. The results demonstrate that sonochemically generated chlorine, known to enhance the electrical conductivity of SWCNT assemblies, also improves interfacial interactions and the adsorption capacity of the nanotubes for TPU leading to significant enhancements in electrical conductivity, Young's modulus, and failure strength of the nanocomposites without compromising ultimate strain. Analysis of effective adsorption isotherms gives new insights into the mechanisms driving interfacial interactions and a model detailing various adsorption regions is proposed. Saturation differences in SWCNT adsorption sites, contingent on processing conditions, account for observed trends and determine the optimal SWCNT/TPU ratio and factors affecting macroscopic properties. Furthermore, insights from effective adsorption isotherms can guide the optimization of the fabrication method to enhance properties.

Controlled adsorption optimizes nanocomposite sheet properties by enhancing interfacial interactions. Effective adsorption isotherms help understand trends, TPU–SWCNT interactions, and factors affecting mechanical properties and conductivity.