## Result and Discussion
### Thermal Stability  
Thermogravimetric analysis (TGA) measurements of the MMT and OMMT samples are shown in Figure 5. As shown in Figure 5, at temperatures below 100 \({}^{\circ}\)C, the mass losses of the MMT and OMMT samples arising from the dehydration of water molecules adsorbed on the clay surfaces and the interlayer spaces were 7.1% and 5.0%, respectively. Moreover, the water content of OMMT was less than that of MMT, which indicated that the absorbed water molecules were partially replaced by the \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Code** & \(M_{\text{n}}\) (\(\times\)10\({}^{5}\)) & \(M_{\text{w}}\) (\(\times\)10\({}^{5}\)) & **PDI** \\ \hline PS & 3.65 & 15.09 & 4.14 \\ PS-OMMT-1 & 1.76 & 7.56 & 4.31 \\ PS-OMMT-3 & 1.56 & 5.57 & 3.57 \\ PS-OMMT-5 & 1.55 & 7.35 & 4.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Molecular weight distribution of PS and PS-OMMT nanocomposites. Figure 4: TEM images of (**A**) PS, (**B**) PS-OMMT-1, (**C**) PS-OMMT-3 and (**D**) PS-OMMT-5. anionic surfactant. During this stage, the SLS molecules were intercalated into the interlayer spaces of the MMT, resulting in a change from a hydrophilic MMT surface to a hydrophobic one. The MMT mass loss in the temperature range of 100-800 \({}^{\circ}\)C, corresponding to dehydroxylation of the MMT, was merely 5.3%, [34]. The total MMT mass loss was approximately 12.4%. In contrast, there was an obvious mass loss in the temperature range of 350-500 \({}^{\circ}\)C for the OMMT samples, which was attributed to the evaporation/decomposition of the loaded anionic surfactants, such that the mass loss reached approximately 11.4%. In the temperature range of 500-800 \({}^{\circ}\)C, the OMMT mass loss arising from dehydroxylation of the MMT layers was approximately 5.3% [34]. The total mass loss of OMMT was approximately 24.0%. As shown above, the total amount of anionic surfactants in the OMMT was close to 70% of mole percent based on the CEC value (i.e., 100 mmol/100 g clay). This result further confirmed that the anionic surfactant was indeed intercalated into the MMT interlayers, as previously indicated by the XRD patterns shown in Figure 3.  
Figure 6 presents TGA traces and derivative thermogravimetry (DTG) results for the pure PS and PS-OMMT nanocomposites. In Figure 6, the nanocomposites showed similar degradation behaviors (curve patterns) as the pure polymer, indicating a similar degradation mechanism to pure PS. Figure 6 shows that the onset degradation temperature (T\({}_{10}\), 10 wt % mass loss) increased from 346.1 \({}^{\circ}\)C for pure PS to 348.7 \({}^{\circ}\)C, 376.2 \({}^{\circ}\)C and 372.8 \({}^{\circ}\)C for the PS-OMMT-1, PS-OMMT-3 and PS-OMMT-5 samples, respectively. The temperatures of the maximum decomposition rate (T\({}_{\text{max}}\)), as revealed by the DTG curves, followed the same trend and increased by 6.7 \({}^{\circ}\)C, 18.1 \({}^{\circ}\)C and 13.0 \({}^{\circ}\)C, respectively, compared with pure PS. These results suggested that the introduction of OMMT improved the thermal stability of the polystyrene, which may be attributed to a labyrinth or barrier effect originating from the high aspect ratio of the clay layers, which can prevent diffusion of the volatile decomposition products out of the polymer in the thermal degradation zone [39]. However, PS-OMMT-3 was found to have the best thermal stability and a 30.1 \({}^{\circ}\)C enhancement in the onset degradation temperature over pure PS. Furthermore, the best enhancement in the T\({}_{\text{max}}\) was also achieved in the PS-OMMT-3 sample. These results were attributed to the higher degree of exfoliation of the clay layers and better dispersion obtained in the PS-OMMT-3 sample than the other samples. It was plausible that the exfoliated and dispersed clay layers played a significant role as nucleating agents in the polymer matrix by limiting the heat transfer, which may enhance the degradation temperature [31].