**A Novel Grafting of Polymers onto the Surface of Graphene Oxide**

Norio Tsubokawa, Takeshi Yamauchi, Kazuhiro Fujiki and Shingo Tamesue

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67477

#### **Abstract**

A simple grafting of polymers onto graphene oxide (GO) was achieved by polymer radical trapping, ligand-exchange reaction, and surface initiated cationic and anionic graft polymerization. Grafting of poly(ethylene glycol) (PEG) onto GO was successfully achieved by trapping of PEG radicals formed by thermal decomposition of PEG macroazo initiator to give PEG-grafted GO. The grafting of copolymers containing vinyl ferrocene moieties onto GO surfaces was also successfully achieved by the ligand-exchange reaction between ferrocene moieties of these copolymers and GO. Carboxyl groups on GO have an ability to initiate the cationic polymerizations of vinyl monomers, such as *N*-vinylcarbazole and isobutyl vinyl ether. The corresponding vinyl polymers were grafted onto GO, during the cationic polymerization, based on the termination of growing polymer cation by counter anion (carboxylate) groups on GO. It was found that the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was successfully initiated by potassium carboxylate groups on GO, introduced by neutralization of carboxyl groups with KOH, to give the corresponding polyester-grafted GO. The dispersibility of GO in organic solvents was remarkably improved by the grafting of the above polymers onto GO. In addition, easy preparation of reduced GO-based conducting polyaniline composite organogel will be discussed.

**Keywords:** graphene, graphene oxide, grafting of polymers, surface-initiated polymerization, ligand-exchange reaction

### **1. Introduction**

Recently, graphene and graphene oxide (GO), as well as carbon nanotube, nanodiamond, and fullerene, have emerged as excellent nanomaterials having electrical and thermal conductive,

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mechanical, gas barrier, optical, and antibacterial properties. Therefore, a polymer composite with GO has recently attracted much interest in the materials field due to its outstanding properties [1–8]. Especially, many researchers have reported the preparation and properties of GO/chitin and GO/biopolymer composites [9–15]. For example, Travlou et al. have reported the synthesis and applications of GO/chitosan and GO/polysaccharides nanocomposites [9, 14].

It is well known that in comparison with GO/chitin nanocomposite, we can obtain GO having an excellent dispersibility into organic solvents and various polymer matrices by grafting of conventional polymers onto GO and readily obtain thermosetting, thermoplastic, and thermoelastic polymer nanocomposite thin films having electro and thermal conductivity. The surface modifications of graphene oxide (GO) by grafting of polymers via atom transfer radical polymerization (ATRP) [4–6, 16, 17] and reverse addition fragmentation chain transfer polymerization (RAFT) have been reported by many researchers [7, 8, 18]. According to the above-mentioned method, polymer brush grafted onto GO can be obtained.

However, the above graft polymerization needs the complicated treatment for the introduction of surface-initiating groups. Therefore, it is desired to develop a simple and an easy method for the grafting of polymers onto GO without complicated procedures for the introduction of the initiating groups onto GO.

On the other hand, we have also achieved the grafting of various polymers onto various nanocarbons such as carbon black, carbon nanotubes, fullerene, and nanodiamond, by "grafting from" and "grafting onto" methods [19, 20]. We have designed a simple surface grafting of various polymers onto these nanocarbons by polymer radical trapping [21, 22], ligand-exchange reaction [23, 24], surface-initiated cationic [25], and anionic graft polymerization [26]. According to the above processes, they do not require complicated process for the introduction of initiating groups onto nanocarbons for the graft polymerization.

In this chapter, a novel and an easy grafting of polymers onto GO without complicated pretreatment by trapping of polymer radicals [27], ligand-exchange reaction of ferrocenecontaining polymer with GO [27], and simple cationic and anionic graft polymerization initiated by carboxyl groups on GO [28] are reviewed. In addition, the dispersibility of various polymer-grafted GO in several organic solvents and easy preparation of conductive composite gel consisting of reduced GO and polyaniline will be discussed.
