**5. Anionic ring‐opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate groups on GO**

#### **5.1. Anionic ring‐opening alternating copolymerization of epoxides with cyclic acid anhydrides**

It is well known that alkali metal salts of aromatic carboxylic acid, such as potassium benzoate, have an ability to initiate the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides to give the corresponding polyester. On the other hand, we have reported, in the previous paper, that potassium carboxylate (COOK) groups introduced onto the surface of nanocarbons, such as carbon black and vapor grown carbon fiber, can initiate the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides and the corresponding polyester is readily grafted these nanocarbon surfaces [19, 20, 26, 28].

#### **5.2. Anionic ring‐opening alternating copolymerization initiated by COOK groups on GO**

The anionic ring-opening alternating copolymerization of styrene oxide (SO) with phthalic anhydride (PAn) initiated by COOK groups on GO (GO-COOK) was examined (**Scheme 5**). GO-COOK can be readily prepared by the neutralization of COOH groups on GO with KOH. **Table 3** shows the results of the anionic ring-opening copolymerization of SO with PAn in the presence of GO-COOK under several conditions. In the polymerization, 18-crown-6 was added as an accelerator of the anionic copolymerization [19, 20, 26, 28].

As shown in **Table 3**, the ring-opening copolymerization of SO with PAn was hardly initiated in the presence of untreated GO (GO-COOH). In addition, no initiation of the anionic ring-opening polymerization of SO (or PAn) was observed even in the presence of GO-COOK. On the other hand, it was found that GO-COOK has an ability to initiate the anionic ring-opening alternating copolymerization of SO with PAn and the corresponding polyester, poly(SO-*alt*-PAn), was grafted onto GO.

The effect of polymerization time on the anionic ring‐opening alternating copolymerization of SO with PAn [or maleic anhydride (MAn)] initiated by GO‐COOK is shown in **Figure 13**. The copolymerization of SO with MAn was carried out in the presence of *N*-phenyl-naphthylamine (NPNA) in order to inhibit the radical cross‐linking of formed unsaturated polyester, poly(SO-*alt*‐MAn). It was found that the conversion increased with elapse of the polymerization time and the conversion of poly(SO-*alt*-PAn) and poly(SO-*alt*‐MAn) exceeded 70 and 50% after 3 h at 120°C, respectively, suggesting the grafting of the corresponding polyester onto GO.

**Scheme 5.** Anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by COOK groups on GO.


**Table 3.** Anionic ring-opening copolymerization of SO with PAn in the presence of GO-COOK and GO-COOH under several conditions.

**Figure 13.** Effect of polymerization time on the anionic ring‐opening alternating copolymerization of SO with PAn and MAn in the presence of GO‐COOK. GO‐COOK, 0.10 g; SO, 0.01 mol; cyclic acid anhydride, 0.01 mol; 18‐crown‐6, 0.02 mol; NPNA (in the case of MAn), 0.02 g, Temp., 120°C.

#### **5.3. Identification of polyester‐grafted GO by GC‐MS**

**5.2. Anionic ring‐opening alternating copolymerization initiated by COOK groups on GO**

The anionic ring-opening alternating copolymerization of styrene oxide (SO) with phthalic anhydride (PAn) initiated by COOK groups on GO (GO-COOK) was examined (**Scheme 5**). GO-COOK can be readily prepared by the neutralization of COOH groups on GO with KOH. **Table 3** shows the results of the anionic ring-opening copolymerization of SO with PAn in the presence of GO-COOK under several conditions. In the polymerization, 18-crown-6 was

As shown in **Table 3**, the ring-opening copolymerization of SO with PAn was hardly initiated in the presence of untreated GO (GO-COOH). In addition, no initiation of the anionic ring-opening polymerization of SO (or PAn) was observed even in the presence of GO-COOK. On the other hand, it was found that GO-COOK has an ability to initiate the anionic ring-opening alternating copolymerization of SO with PAn and the corresponding polyester, poly(SO-*alt*-PAn), was

The effect of polymerization time on the anionic ring‐opening alternating copolymerization of SO with PAn [or maleic anhydride (MAn)] initiated by GO‐COOK is shown in **Figure 13**. The copolymerization of SO with MAn was carried out in the presence of *N*-phenyl-naphthylamine (NPNA) in order to inhibit the radical cross‐linking of formed unsaturated polyester, poly(SO-*alt*‐MAn). It was found that the conversion increased with elapse of the polymerization time and the conversion of poly(SO-*alt*-PAn) and poly(SO-*alt*‐MAn) exceeded 70 and 50% after 3 h at 120°C, respectively, suggesting the grafting of the corresponding polyester

**Scheme 5.** Anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by

added as an accelerator of the anionic copolymerization [19, 20, 26, 28].

18 Graphene Materials - Structure, Properties and Modifications

grafted onto GO.

onto GO.

COOK groups on GO.

**Figure 14(A)** shows thermal decomposition GC of poly(SO-*alt*-PAn), which is obtained by using the conventional catalyst, GO-COOK, and GO-*g*-poly(SO-*alt*-PAn), obtained from the anionic ring-opening alternating copolymerization in the presence of GO-COOK. As shown in **Figure 14(A)**, the thermally decomposed gas of GO-*g*-poly(SO-*alt*-PAn) generated at retention time at 2.0 and 4.8 min was in accord with those of poly(SO-*alt*-PAn). In addition, the MS of thermally decomposed gas of poly(SO‐*alt*-PAn) and GO-*g*-poly(SO-*alt*-PAn) at retention time 2.0 and 4.8 min, respectively, is shown in **Figure 14(B)** and **(C)**. It was found that the MS of thermally decomposed gas of poly(SO‐*alt*-PAn)-grafted GO at retention time 2.0 min was in accord with that of poly(SO-*alt*-PAn), as shown in **Figure 14(B)**: the parent peak at 104 (m/z) was estimated to be the corresponding styrene generated by the thermal

**Figure 14.** (A) Thermal decomposition gas chromatograms of (1) GO-*g*-poly(SO-*alt*-PAn), (2) poly(SO-*alt*-PAn), and (3) GO. (B) and (C) Mass spectra of thermal decomposition gas of GO‐*g*-poly(SO-*alt*-PAn) and poly(SO-*alt*-PAn) at retention time 2.0 min and 4.8 min, respectively.

decomposition of poly(SO-*alt*‐PAn). Furthermore, the MS of thermally decomposed gas of GO-*g*-poly(SO-*alt*-PAn) at retention time 4.8 min agreed with that of poly(SO-*alt*-PAn), as shown in **Figure 14(C)**; the parent peak at 148 (m/z) is estimated to be PAn generated by the thermal decomposition of poly(SO-*alt*‐PAn). Based on the above results, it is concluded that poly(SO-*alt*-PAn) was successfully grafted onto GO during the anionic ring-opening copolymerization initiated by GO-COOK.

It was also confirmed by GC‐MS that the grafting of poly(SO‐*alt*‐MAn) onto GO successfully achieved by the anionic ring‐opening alternating copolymerization of SO with MAn initiated by GO-COOK.

### **6. Dispersibility of polymer‐grafted GO in solvents**

#### **6.1. Dispersibility of GO obtained from radical trapping and ligand‐exchange reaction**

The untreated GO, GO-*g*-PEG, and GO-*g*-poly(Vf-*co*‐MMA) were dispersed in good solvent of````` grafted polymer under irradiating ultrasonic wave and allowed to stand at room temperature. As a result, untreated GO precipitated within 15 min, but the dispersion of GO-*g*-PEG and GO-*g*-poly(Vf-*co*‐MMA) in THF has excellent stability and precipitation of GO was scarcely observed even after 1 week at room temperature.

The stability of the GO dispersion in THF after the ultrasonic wave irradiation was also examined from the decrease of absorbance of GO dispersion at room temperature by use of UV-Vis spectrometer. The higher absorbance indicates no precipitation of GO, but lower absorbance indicates the precipitation of GO. As shown in **Figure 15**, untreated GO immediately precipitated, but the precipitation of GO-*g*-PEG and GO-*g*-poly(Vf-*co*‐MMA) was scarcely observed, indicating the effect of grafting of polymers onto GO.

The results suggest that by the grafting of PEG and poly(Vf-*co*‐MMA) onto GO surfaces, theaggregation of GO was successfully destroyed and grafted polymer chains onto the surface interfere with reaggregation of the GO in good solvents for grafted polymer, such as THF.

#### **6.2. Dispersibility of GO obtained from surface‐initiated cationic and anionic polymerization**

decomposition of poly(SO-*alt*‐PAn). Furthermore, the MS of thermally decomposed gas of GO-*g*-poly(SO-*alt*-PAn) at retention time 4.8 min agreed with that of poly(SO-*alt*-PAn), as shown in **Figure 14(C)**; the parent peak at 148 (m/z) is estimated to be PAn generated by the thermal decomposition of poly(SO-*alt*‐PAn). Based on the above results, it is concluded that poly(SO-*alt*-PAn) was successfully grafted onto GO during the anionic ring-opening copoly-

**Figure 14.** (A) Thermal decomposition gas chromatograms of (1) GO-*g*-poly(SO-*alt*-PAn), (2) poly(SO-*alt*-PAn), and (3) GO. (B) and (C) Mass spectra of thermal decomposition gas of GO‐*g*-poly(SO-*alt*-PAn) and poly(SO-*alt*-PAn) at

It was also confirmed by GC‐MS that the grafting of poly(SO‐*alt*‐MAn) onto GO successfully achieved by the anionic ring‐opening alternating copolymerization of SO with MAn initiated

**6.1. Dispersibility of GO obtained from radical trapping and ligand‐exchange reaction**

The untreated GO, GO-*g*-PEG, and GO-*g*-poly(Vf-*co*‐MMA) were dispersed in good solvent of````` grafted polymer under irradiating ultrasonic wave and allowed to stand at room temperature. As a result, untreated GO precipitated within 15 min, but the dispersion of GO-*g*-PEG and GO-*g*-poly(Vf-*co*‐MMA) in THF has excellent stability and precipitation of GO was scarcely

**6. Dispersibility of polymer‐grafted GO in solvents**

observed even after 1 week at room temperature.

merization initiated by GO-COOK.

retention time 2.0 min and 4.8 min, respectively.

20 Graphene Materials - Structure, Properties and Modifications

by GO-COOK.

**Figure 16** shows the stability of dispersion of ungrafted GO, GO-*g*‐polyNVC, GO‐*g*‐polyIBVE, and GO*-g-*poly(SO-*alt*-PAn) in THF at room temperature. Ungrafted GO precipitated completely within 3 h. On the contrary, polymer-grafted GOs gave stable dispersions in THF, a good solvent for grafted polymers.

Therefore, it is concluded that dispersibility of GO in THF was remarkably improved by grafting of polymers, such as polyNVC, polyIBVE, and polyesters.

**Figure 15.** Dispersibility of GO-*g*-PEG and GO-*g*-poly(Vf-*co*‐MMA) in THF at room temperature.

**Figure 16.** Dispersibility of ungrafted GO, GO-*g*‐polyNVC, GO‐*g*‐polyIBVE, GO‐*g*-poly(SO-*alt*-PAn) in THF at room temperature.
