Horacio J. Salavagione

Recent Advances in the Covalent Modification of Graphene With Polymers

Covalent binding of polymers to graphene represents an interesting alternative for the development of novel composite materials with a compendium of interfacial interactions. Through covalent linking, the concept of interface changes from a traditional view of interactions between components, such as van der Waals, hydrogen bonding, and so on, that is to say, at a polymer-filler interface, to a single compound concept where graphene forms an integral part of the polymeric chains. This feature article provides an overview of the strategies currently employed to functionalize graphene with polymers. We focus on the grafting-from and grafting-to methods used to bind polymers to graphene. The advantages and drawbacks, as well as the influence of each method on the final properties, are highlighted.

Synthesis of poly(vinyl alcohol)/reduced graphite oxide nanocomposites with improved thermal and electrical properties

Poly(vinylalcohol)/reduced graphite oxide nanocomposites have been synthesised by reducing graphite oxide in the presence of the polymer matrix and coagulating the system with 2-propanol. It has been observed that some interactions occur between the polymer and the reduced graphite oxide layers, mainly by hydrogen bonding. These interactions are responsible for a remarkable change in the thermal behaviour of the nanocomposites. In addition, high electrical conductivity has been achieved at concentrations beyond 7.5 wt% of reduced graphite oxide (∼0.1 S cm−1), with a percolation threshold between 0.5 and 1 wt%.

Chemical sensors based on polymer composites with carbon nanotubes and graphene: the role of the polymer

This review provides an overview of recent research on chemical sensors based on polymer composites with carbon nanotubes (CNTs) and graphene (G) for quantitative and qualitative analysis in diverse application fields such as biosensing (DNA, enzymes, proteins, antigens and metabolites), and chemical and gas sensing using electrochemical and optical detection methods. Both CNTs and G show outstanding electrical, chemical, electrochemical and optical properties that make them ideal candidates for use in chemical sensors. The incorporation of polymers into the development of this type of sensor not only improves the CNT and G dispersion, but also enhances some of their properties like redox behaviour and biocompatibility, and provides additional properties such as photoelectric or swelling capacity. Moreover, unique synergistic effects arising from the combination of the matrix and nanofiller contributions are described by means of several examples highlighting the most important achievements in this field. Special emphasis has been placed throughout the review on analysing the role of the polymer in different sensing platforms. The combination of polymers with carbon nanomaterials for the preparation of chemical sensors opens up exciting areas of research due to their biocompatibility, and excellent sensitivity and selectivity.

Graphene functionalisation with a conjugated poly(fluorene) by click coupling: striking electronic properties in solution.

Graphene flakes covalently modified with a conjugated polymer, poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis-(6-azidohexyl)fluorene)] (PFA), were efficiently synthesised by a Cu-catalysed Huisgen 1,3-dipolar cycloaddition between alkyne-modified graphene and an azide-functionalised polymer. Two approaches for the modification of graphene with alkyne groups were investigated (coupling with a diazonium salt generated in situ or an amidation reaction) and the optimum conditions determined. The success of the click-coupling approach was confirmed by FTIR, (1)H NMR, Raman, and X-ray photoelectron spectroscopy (XPS). The absorption and emission spectra of the click product show a strong solvent dependency.

A versatile chemical tool for the preparation of conductive graphene-based polymer nanocomposites

A general route for the functionalization of graphene and graphene derivatives with a low molecular weight polymer by thiol-radical reactions is reported. Polymer-modified graphene is employed as a filler for high density polyethylene to generate materials with good electrical conductivity.

Promising alternative routes for graphene production and functionalization

A decade after scientists from Manchester University isolated a single graphene sheet, the development of a method for mass-scale production of graphene of a similar quality to that obtained, and the implementation of a modular chemical route to incorporate graphene into multicomponent/multifunctional materials are still fundamental challenges. The methods for graphene production and the synthetic procedures for its modification are limited to a handful of established methodologies, each with important limitations. In this manuscript a non-conventional electrochemical method for the preparation of high-quality graphene, and a recently reported general chemical approach for graphene functionalization through thiol–ene click reactions are highlighted.

Synthesis, properties and aplications of functionalized polyanilines

Novos polimeros condutores funcionalizados foram sintetizados a partir de modificacoes das reacoes de acoplamento polianilina-diazonio, adicao nucleofilica e N-nitrosacao. O acoplamento de diazonio fornece polimeros modificados que sao eletroativos e soluveis em solventes comuns. Adicao nucleofilica tambem pode ser usada para modificacoes da polianilina. Polimeros modificados pela adicao de tiois, carbânions e acidos arilsulfinicos sao apresentados. A adicao nucleofilica de acidos arilsulfinicos a polianilina oxidada mostrou ser controlada pelos estados de oxidacao e/ou protonacao do polimero. A N-nitrosacao de polianilina tambem e possivel, produzindo material soluvel em solventes comuns. Esta reacao pode ser revertida por tratamento acido. A reacao de nitrosacao reversivel foi usada para controlar processos litograficos e fotolitograficos de deposicao de padroes de PANI.

Supramolecular assembly of graphene with functionalized poly(fluorene-alt-phenylene): the role of the anthraquinone pendant groups

Hybrid materials composed of graphene and conjugated poly(fluorene-alt-phenylene) endowed with redox-active anthraquinone moieties are prepared. Remarkable changes in the electronic properties of the polymer are observed. Effective interactions among the pendant anthraquinone and graphene, likely due to π-π stacking, are confirmed.

Identification of high performance solvents for the sustainable processing of graphene

Nanomaterials have many advanced applications, from bio-medicine to flexible electronics to energy storage, and the broad interest in graphene-based materials and devices means that high annual tonnages will be required to meet this demand. However, manufacturing at the required scale remains unfeasible until economic and environmental obstacles are resolved. Liquid exfoliation of graphite is the preferred scalable method to prepare large quantities of good quality graphene, but only low concentrations are achieved and the solvents habitually employed are toxic. Furthermore, good dispersions of nanomaterials in organic solvents are crucial for the synthesis of many types of nanocomposites. To address the performance and safety issues of solvent use, a bespoke approach to solvent selection was developed and the renewable solvent Cyrene was identified as having excellent properties. Graphene dispersions in Cyrene were found to be an order of magnitude more concentrated than those achieved in N-methylpyrrolidinone (NMP). Key attributes to this success are optimum solvent polarity, and importantly a high viscosity. We report the role of viscosity as crucial for the creation of larger and less defective graphene flakes. These findings can equally be applied to the dispersion of other layered bi-dimensional materials, where alternative solvent options could be used as drop-in replacements for established processes without disruption or the need to use specialized equipment. Thus, the discovery of a benign yet high performance graphene processing solvent enhances the efficiency, sustainability and commercial potential of this ever-growing field, particularly in the area of bulk material processing for large volume applications.

“Click”-Functionalization of [60]Fullerene and Graphene with an Unsymmetrically Functionalized Diketopyrrolopyrrole (DPP) Derivative

A synthetic strategy is developed that allows for the facile functionalization of carbon nanostructures thus providing the possibility of comparing the striking different optical and electrochemical properties of ensembles based on the diketopyrrolopyrrole (DPP) chromophore covalently attached to either [60]fullerene or graphene.