# Comparison of the Properties and Structure of Montmorillonite Modified with Polyvinylpyrrolidone
## 3 Results and Discussion  
### Crystal Structure of the Modified MMT  
The X-ray diffraction patterns for the studied samples are shown in Figures 1-3. The original MMT (Figure 1, curve a) has a typical MMT crystal structure. All main characteristic reflections are present, including montmorillonite reflections: M(001) at 2\(\Theta\) = 8.79, M(002) at 2\(\Theta\) = 17.71, M(110) at 2\(\Theta\) = 19.77, M(220) at 2\(\Theta\) = 34.91 and quartz reflections: Q(101) at 2\(\Theta\) = 26.59, Q(112) at 2\(\Theta\) = 45.44. Identical reflections are present in the diffractograms of all MMT/PVP-bottom samples (Figure 1) regardless of the MMT/PVP ratio in the original mixture, however, their position and intensity differ significantly. For example, the MMT/PVP-bottom sample at the MMT:PVP ratio 1:2 (Figure 1, curve f) is characterized by a shift of all characteristic reflections towards smaller 2\(\Theta\) angles and a decrease in their intensity. This indicates the entry of PVP macromolecules into the interlayer space of MMT, that is, its intercalation. The formation of an intercalated structure in the sample was confirmed in a previous work [46]. At other ratios of MMT and PVP, all the characteristic reflections in the MMT/PVP-bottom samples are shifted towards  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**MMT:PVP Ratio**} & \multicolumn{3}{c}{**Fractions Yield, [\%]**} \\ \cline{2-4}  & **MMT/PVP-Bottom** & **MMT/PVP-Middle** & **MMT/PVP-Top** \\ \hline
4:1 & \(35\pm 1\) & \(56\pm 1\) & \(7\pm 1\) \\ \hline
3:1 & \(31\pm 1\) & \(55\pm 1\) & \(11\pm 1\) \\ \hline
2:1 & \(28\pm 1\) & \(48\pm 1\) & \(20\pm 1\) \\ \hline
1:1 & \(24\pm 1\) & \(38\pm 1\) & \(34\pm 1\) \\ \hline
1:2 & \(20\pm 1  
In the MMT/PVP-middle samples, all characteristic MMT reflections are slightly shifted towards larger 2\(\Theta\) angles, regardless of the ratio of components (Figure 2, curves b-f). The appearance of these diffraction patterns differs from the pure MMT. Individual MMT reflections disappear, and PVP reflections appear. The intensity of M(001), M(002), and Q(101) reflections of these samples depends on the MMT/PVP ratio and is the highest for samples of pure MMT and MMT/PVP = 1:2. It can be argued that all MMT/PVP-middle samples have a flocculated structure (partially intercalated and exfoliated structure) [46] regardless of the initial ratio of components. It can be assumed that the MMT/PVP-middle = 3:1 contains the least amount of intercalated MMT. This is confirmed by the very low intensity of the M(001) reflection (Figure 2, curve c). The diffractograms of samples MMT/PVP = 1:12 (Figure 3, curve a), MMT/PVP-top (Figure 3, curve b), and pure PVP (Figure 3, curve c) are almost identical. It is worth noting that the initial MMT/PVP ratio almost does not affect the appearance of the MMT/PVP-top diffractogram therefore Figure 3 shows only the diffractogram of the MMT/PVP-top at the MMT:PVP ratio 1:2. The M(001) reflection at 2\(\Theta\) = 8.79\({}^{\circ}\), which characterizes the interlayer space in MMT, is absent in the MMT/PVP-top and MMT/PVP = 1:12. This indicates almost complete exfoliation of MMT in these samples. However, it is possible to highlight some differences in the diffractograms of these samples. The diffraction pattern of the MMT/PVP-top sample (Figure 3, curve b) shows reflections M(110) at 2\(\Theta\) = 19.72\({}^{\circ}\) and M(220) at 2\(\Theta\) = 34.81\({}^{\circ}\), which are characteristic of MMT at 2\(\Theta\) = 19.77\({}^{\circ}\) and 2\(\Theta\) = 34.91\({}^{\circ}\), respectively (Figure 1, curve a). These reflections are absent in the PVP and MMT/PVP = 1:12, and in the MMT/PVP-top sample, they are shifted to the area of smaller 2\(\Theta\) angles compared to pure MMT. In the MMT/PVP = 1:12 sample, there is a Q(101) reflection at 2\(\Theta\) = 26.79\({}^{\circ}\) (Figure 3, curve a), which is characteristic of MMT at 2\(\Theta\) = 26.59\({}^{\circ}\) (Figure 1, curve a). This reflection is absent in PVP and MMT/PVP-top.