Progress in Imidazolium Ionic Liquids Assisted Fabrication of Carbon Nanotube and Graphene Polymer Composites

Yuanzhen Wang,Wei Tang,Rengui Peng,Yingkui Yang,Xiaolin Xie

doi:10.3390/polym5020847

Abstract

Carbon nanotubes (CNTs) and graphene sheets are the most promising fillers for polymer nanocomposites due to their superior mechanical, electrical, thermal optical and gas barrier properties, as well as high flame-retardant efficiency. The critical challenge, however, is how to uniformly disperse them into the polymer matrix to achieve a strong interface for good load transfer between the two. This problem is not new but more acute in CNTs and graphene, both because they are intrinsically insoluble and tend to aggregate into bundles and because their surfaces are atomically smooth. Over the past decade, imidazolium ionic liquids (Imi-ILs) have played a multifunctional role (e.g., as solvents, dispersants, stabilizers, compatibilizers, modifiers and additives) in the fabrication of polymer composites containing CNTs or graphene. In this review, we first summarize the liquid-phase exfoliation, stabilization, dispersion of CNTs and graphene in Imi-ILs, as well as the chemical and/or thermal reduction of graphene oxide to graphene with the aid of Imi-ILs. We then present a full survey of the literature on the Imi-ILs assisted fabrication of CNTs and graphene-based nanocomposites with a variety of polymers, including fluoropolymers, hydrocarbon polymers, polyacrylates, cellulose and polymeric ionic liquids. Finally, we give a future outlook in hopes of facilitating progress in this emerging area.

Highlights

Incorporation of nanosized fillers into polymers has created new composites by expanding the functions and applications while retaining the excellent manufacturing and processing flexibility inherent to polymers [1,2]
carbon nanotubes (CNTs) are structurally constructed by rolling-up a single or multi graphene sheets into a seamless cylindrical tube, and they are classified into single-walled CNTs (SWCNTs) or multi-walled CNTs (MWCNTs) [9,10,11], respectively
We have found that MWCNTs functionalized by organic molecules [42,43], polystyrene (PS) [44,45], hyperbranched poly(urea-urethane) [46,47], biodegradable poly(ε-caprolactone) (PCL) [48,49], azobenzene-containing polyurethane [50] and ionic polymers [51] are well soluble in water or organic solvents

Summary

Introduction

Incorporation of nanosized fillers into polymers has created new composites by expanding the functions and applications while retaining the excellent manufacturing and processing flexibility inherent to polymers [1,2]. The Young’s modulus, storage modulus and tensile strength of neat epoxy are increased by 28.4%, 23.8%, and 22.9%, respectively, by adding 0.5 wt % of l-MWCNTs. The functionalized CNTs in liquid form contribute to better dispersion and superior interfacial bonding with the matrix, thereby facilitating greater mechanical reinforcement efficiency. Of special interest here is the fabrication of nanotube and graphene polymer composites assisted by imidazolium-based ionic liquids (Imi-ILs). The Imi-ILs assisted fabrication of polymer composites with CNTs and graphene has triggered an increasing attention [63]; a comprehensive review is still absent from the literatures. Exfoliation of Carbon Nanotubes and Graphene Sheets in Imidazolium Ionic Liquids

Carbon Nanotubes in Imidazolium Ionic Liquids

Graphene Sheets in Imidazolium Ionic Liquids

With Carbon Nanotubes

With Graphene

Findings

Conclusions