| Summary: | 碩士 === 國立中興大學 === 化學工程學系所 === 102 === The purpose of this research is the graphene oxide (GO) can be prepared from natural graphite by the modified Hummers method from natural expanded graphite. Dimethylformamide (DMF) solvent is considered a good candidate for th prevention of irreversible graphene sheet aggregation during the hydrazine reduction of GO. A facile approach was used to prepare the GO and RGOD supported polypyrrole (PPy) nanoparticles via the in situ chemical oxidative polymerization of pyrrole (Py) onto the surfaces of the GO and RGOD modified with dodecylbenzenessulfonic acid sodium salt (DBSNa) or sodium polystyrene 4-sulfonate (PSS) as a dopant for PPy. The electrical conductivity、thermal stability、structure characteristics and morphology are investigated in this
research.
In this study, the preparation of composites through in situ polymerization technique employing Py monomer and graphene was done with two kinds of composites synthesized. For system (I), PPy/GO composites, were chemically synthesized in water solution by decorating PPy nanoparticles onto the surfaces of the GO via facile in situ oxidation polymerization of potassium persulfate (KPS) by using DBSNa and PSS as an anionic dopant. The composites were prepared by in situ polymerization involving Py and GO with the dopant, DBSNa. The weight feed ratio of Py to GO was 100/1 which polymerize for 1hour、2hour、3hour and 4hour. The weight feed ratio of Py to GO was 5/1 which polymerize for 1hour、2hour and 3hour. The weight feed ratio 100/1 and 5/1 resulting composites were designated as D/100P/GO-K-a-1h、D/100P/GO-K-a-2h、D/100P/GO-K-a -3h and D/100P/GO-K-a-4h and D/5P/GO-K-a-1h、D/5P/GO-K-a-2h and D/5P/GO-K-a-3h ; while the composites were prepared by in situ polymerization involving Py and GO with the dopant, PSS. The weight feed ratio of Py to GO was 5/1, 3/1, and 1/1. Each of them polymerize for 1hour、2hour and 3hour. The weight feed ratio 5/1, 3/1 and 1/1 resulting composites were designated as S/5P/GO-K-a-1h、S/5P/GO-K-a-2h and
S/5P/GO-K-a-3h, S/3P/GO-K-a-1h、S/3P/GO-K-a-2h and S/3P/GO-K-a-3h, and S/1P/GO-K-a-1h、S/1P/GO-K-a-2h and S/1P/GO-K-a-3h. For system (II) is PPy/RGOD composites chemically synthesized in DMF solvent by decorating PPy nanoparticles onto its surfaces of the RGOD via the in situ oxidation polymerization of the oxidant by using PSS as an anionic dopant.The oxidant, such as KPS and ferric Chloride (FeCl3). The composites were prepared by in situ polymerization involving Py and RGOD with dopant of PSS and oxidant of KPS. The weight feed ratio of Py to RGOD was 5/1 and the molar feed ratio of Py to KPS was 1/0.58 which polymerize for 1hour、2hour and 3hour. The resulting composites were designated as S/5P/RGO-K-d-1h、S/5P/RGO-K-d-2h and S/5P/RGO -K-d-3h; while the composites were prepared by in situ polymerization involving Py and RGOD with the dopant, PSS, and the oxidant, FeCl3. The weight feed ratio of Py to RGOD was 5/1 and the molar feed ratio of Py to FeCl3 was varied as 1/0.5, 1/0.75, and 1/1. Each of them polymerize for 1hour、2hour and 3hour. The molar feed ratio of Py to FeCl3 was 1/0.5, 1/0.75, and 1/1 resulting composites were designate as S/5P/RGO-0.5Fe-d- 1h、S/5P/RGO-0.5Fe-d-2h and S/5P/RGO-0.5Fe-d-3h, S/5P/RGO-0.75Fe- d-1h、S/5P/RGO-0.75Fe-d-2h and S/5P/RGO-0.75Fe-d-3h, and S/5P/RGO
-1Fe-d-1h、S/5P/RGO-1Fe-d-3h and S/5P/RGO-1Fe-d-3h.
As show in the FTIR spectra of PPy/graphene nanocomposites, all the results demonstrate almost at the same peak positions of the main IR bands which are associated with the structure of the PPy. The peaks at 1545 and 1457 cm-1, which could be attributed to C-N and C-C asymmetric and symmetric ring-stretching. The breathing vibration of pyrrole ring occur at 1174 cm-1, 1091 cm-1 for NH2+ in-plane deformation stretching vibration, 1040 cm-1 for C-H and N-H in-plane deformation stretching vibration, and 905 cm-1 for C-H out of plane deformation stretching vibration. According to XRD analysis, the diffraction peak of pure GO appears at 2θ = 9.1°. It corresponds to a d-spacing of 0.97 nm with the XRD pattern of D/100P/GO -K-a-4h, D/5P/GO-K-a-3h, S/5P/GO-K-a-3h, and S/3P/GO-K-a-3h that their characteristic diffraction peaks of GO vanished. Besides, there is no apparent diffraction peak at 2θ = 1.5 °~10°. For the S/1P/GO-K-a-3h composite, the peak at 2θ = 9.1°(d = 0.97 nm) had as significant decrease in peak intensity. After hydrazine reduction, the diffraction peak of RGOD became extremely broad and shifted to wider angles up to 23.6°, which is approximately the peak of Graphite. However, it is evidence from the XRD pattern of the S/5P/RGO-K-d-3h, S/5P/RGO-0.5Fe-d-3h, S/5P/RGO-0.75 Fe-d-3h and S/5P/RGO-1Fe-d-3h composites that the peak is at 9.1° and has been disappeared completely indicating the reduction of the GO to RG OD. Pure PPy displays a broad band at 2θ = 20 °~30°. Thermogravimetric analysis shows nearly a 19.3 % weight loss of GO has occurred at 200 oC.
The enhancement of the thermal stability of the PPy/GO composites can be attributed to the increasing dopant which promoted its thermal stability of PPy. As compared of the PPy/GO composites, 5.5 %, 16.1 %, 15.9 %, 17.4 % , and 17.2 % weight losses have been observed for the D/10 0P/GO-K-a- 4h, D/5P/GO-K-a-3h, S/5P/GO-K-a-3h, S/3P/GO-K-a-3h, and S/1P/GO-K -a-3h composites respectively. On the other hand, the weight losses of PPy in the PPy/RGOD composites, 11.1 %, 15.8 %, 11.7 % and 11.8 % weight losses have been observed for the S/5P/RGO-K-d-3h, S/5P/ RGO-0.5Fe-d-3h, S/5P/RGO-0.75Fe-d-3h, S/5P/RGO-1Fe-d-3h composites as a comparison for the PPy/GO composites which justified the improved thermal stability upon the PPy/RGOD composites. Static water contact angle measurement show contact angles for Composites (I) by increasing with Py fraction with its angles are 75.9 °, 61.3 °and 51.8 °and the resulting composites were designated as S/5P/GO-K-a-3h, S/3P/GO-K -a-3h and S/1P/GO-K-a-3h. Through four point probe resistivity measurement, it shows the conductivity for Composites (I). For D/100P/G O-K-a-4h and D/5P/GO-K-a-3h, the conductivities are 5.74 and 15.62 S/cm. For S/5P/GO-K-a-3h, S/3P/GO-K-a-3h and S/1P/GO-K-a-3h, the conductivities are 27.02, 11.39 and 10.37 S/cm. The optimal conductivity as the 5-fold Py fraction is with the dopant PSS. The conductivity of the PPy/RGOD composites, 3.67×10-1, 20.83, 12.05 and 3.07 S/cm are observed by the S/5P/RGO-K-d-3h, S/5P/RGO-0.5Fe-d-3h, S/5P/RGO-0.7 5Fe-d-3h, and S/5P/RGO-1Fe-d-3h composites. The optimal conductivity as molar feed ratio of Py to FeCl3 was 1/0.5 with the oxidant as FeCl3. Through SEM analysis, it reveals that for system (I), the PPy/GO composites, that its PPy particles shaped irregularly sphere aggregated as decreasing with Py fraction and the amount. for system (II), the PPy/RGOD composite, S/5P/RGO-0.5Fe-d-3h, shows that PPy are uniformly wrapped
on RGOD with fiber structure.
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