# Fabrication and Characterization of Modified Graphene Oxide/PAN Hybrid Nanofiber Membrane
## 3 Results
### Characterization of Synthesized Graphene Oxide (GO)
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Name** & **Biggest Pore Size** & **Smallest Pore Size** & **Average Pore Size (nm)** & **Thickness (\(\upmu\)m)** \\ \hline PAN & 459.5 & 169.5 & 213.3 & 77 \(\pm\) 3 \\ \hline GP01 PAN & 474.2 & 171.2 & 226.3 & 79 \(\pm\) 2 \\ \hline GP02 PAN & 484.5 & 175.5 & 232.7 & 81 \(\pm\) 2 \\ \hline GP03 PAN & 473.3 & 183.2 & 243.5 & 83 \(\pm\) 3 \\ \hline GP04 PAN & 482.2 & 194.3 & 245.5 & 84 \(\pm\) 2 \\ \hline GP10 PAN & 485.5 & 243.6 & 269.3 & 88 \(\pm\) 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Pore size and thickness of polyacrylamide(PAN), graphene oxide modified by polydiallyldimeethylammonium chloride/polyacrylamideonitrile (GP/PAN) nanofiber membranes. Figure 4: Digital photos of polyacrylamide(PAN), graphene oxide modified by polydiallyldimethylammonium chloride/polyacrylamideonitrile (GP/PAN) hybrid nanofiber membranes; (**a**) PAN nanofiber membrane, (**b**) GP01 PAN, (**c**) GP02 PAN, (**d**) GP03 PAN, (**e**) GP04 PAN, (**f**) GP10 PAN. Figure 5: Scanning electron microscopy (SEM) images of polyacrylamide(PAN), graphene oxide modified by polydiallydimethylammonium chloride/polyacrylamideonitrile (GP/PAN) hybrid nanofiber membranes; (**a**) PAN nanofiber membrane, (**b**) GP01 PAN, (**c**) GP02 PAN, (**d**) GP03 PAN, (**e**) GP04 PAN, (**f**) GP10 PAN. stronger specific GO functional group peaks (3200 cm\({}^{-1}\) (OH peak), 1740 cm\({}^{-1}\) (C=O), 1630 cm\({}^{-1}\) (C=C), 1226 cm\({}^{-1}\) (C-O), 1040 cm\({}^{-1}\) (C-O-C)) in the FT-IR spectra [36; 37]. Also, in Figure 7, the contact angle results display an obvious decrease trend due to the various hydrophilic functional groups in the GO, which have also been checked in the FT-IR and some earlier published work [36; 38]. The thermal stability of the PAN nanofiber membrane and GP/PAN hybrid nanofiber membranes is shown in Figure 8. Only two samples were measured. Under pyrolytic conditions, the PAN nanofiber membrane with and without nanofillers degraded in two steps. Compared with the PAN nanofiber membrane, the onset thermal decomposition temperature was increased from 300 \({}^{\circ}\)C to 340 \({}^{\circ}\)C. It could thus be concluded that with the addition of GP, the thermal stability of the nanofiber membrane increased. The noticeable improvement of the thermal stability could be contributed to both the original property of GO and the surface modified with PDDA. Figure 6: Fourier-transform infrared spectroscopy (FT-IR) spectra of graphene oxide modified by polydiallyldimethylammonium chloride/polyacrylamideonitrile (GP/PAN) hybrid nanofiber membranes. Figure 7: Contact angle of polyacrylamide(PAN), graphene oxide modified by polydiallyldimethylammonium chloride/polyacrylamideonitrile (GP/PAN) hybrid nanofiber membranes; (**a**) PAN nanofiber membrane, (**b**) GP01 PAN, (**c**) GP02 PAN, (**d**) GP03 PAN, (**e**) GP04 PAN, (**f**) GP10 PAN. Figure 9 shows the stress-strain curves of the PAN nanofiber membrane and series of the GP/PAN hybrid nanofiber membranes. Overall, the tensile strength of all hybrid nanofiber membranes had obviously improved, compared to the PAN nanofiber membrane. However, when the GP content increased to \(>\) 0.4 wt.%, the hybrid nanofiber membrane appeared to have a little lower stress, due to the reduction of the dispersion. When the GP content is more than 0.4 wt.%, it will be difficult to disperse uniformly in the PAN precursor solutions. Consequently, the beaded structures will be formed in the hybrid nanofiber membrane, which can also be confirmed in the SEM images of Figure 5f [26; 37].