3.1.2. X-ray Diffraction

The distances between the clay layers for the raw clay, NaC, OC, and PCN films were obtained from the peak position of the XRD pattern using Bragg's equation:

$$2\mathbf{d}\sin\theta = \mathbf{n}\,\lambda\,\tag{1}$$

where d is the basal spacing between the clay layers; θ is the angle from the diffraction beam to the atomic plane; n (equal to one here) relates to the order of the reflection; λ is the wavelength of the X-ray radiation employed in the experiment (λ = 1.54060 Å).

#### X-ray Diffraction of RC, NaC, and OC

In Figure 6 the spectra of the raw Indian clay (CCIn) showed a characteristic peak at a 2θ value of 7.15◦, corresponding to a basal spacing of 12.35 Å. The small peak in NaC appeared at a 2θ value of 9.17◦, with a d-spacing of 9.64 Å. However, the NaCIn peak after

modification with a CPC organic surfactant to obtain in the OCIn shifted to a lower 2θ value at 4.21◦, with a d-spacing equal to 21 Å due to the loss of water molecules. The XRD patterns for the local Khulays clay (RCKh) in Figure 7 show the characteristic peak of d-spacing at a 2θ equal to 7.00◦ (d = 12.62 Å). This peak in the NaCKh and OCKh was observed at a 2θ equal to 7.39◦ (d = 11.95 Å) and 2θ equal to 4.30◦ (d = 20.55 Å), respectively. The changes and shifting of the OC peaks (for the Indian and Khulays clay) to a lower 2θ and the increase in the d-spacing refer to the increase in the gap between the clay platelets. Thus, the large increase between the NaC platelets provides a good interlayer exchange of sodium cations by CPC cations [34], which means that the CPC surfactant was successfully intercalated in these types of clay [34,36].

**Figure 6.** XRD patterns for RC, NaC, and OC of commercial Indian clay.

#### X-ray Diffraction of PS, OC, and PCN

The XRD of the PCN samples from both clay types are shown in Figures 8 and 9. Both figures show the amorphous PS humps. Low crystallinity is the factor behind the broad diffraction peaks in PS. In the 1–5% PCN patterns, the diffraction peak of polystyrene appeared in the same position in these PCNs (1–5% PCNs). Importantly, the diffraction peak of the OC disappeared in the prepared PCNs, which indicated the amorphous PCN structure. The elimination of the OC peak denotes a significant opening of the clay layers, which is consistent with a good intercalation between the OC and PS matrix. The produced PCNs thus acquired an exfoliated structure. Our findings are consistent with numerous earlier investigations that found polymer clay nanocomposites to have an exfoliated structure [34,36]. The intercalated organic cations can be distinguished based on their different configurations using the d001 spacing value that Chen et al. [37] previously published. The change in the basal spacing for both types of OC is attributed to the increase in the interlayer space distance, indicating a successful intercalation of surfactant molecules between clay layers for both CCIn and RCKh [38,39].

**Figure 7.** XRD patterns for RC, NaC, and OC of Khulays clay.

**Figure 8.** XRD patterns of pure OC, pure PS, and 1–5% wt. PCN using Indian organoclay.

**Figure 9.** XRD patterns of pure OC, pure PS, and 1–5% PCN using Khulays organoclay.
