# Thermo-Regulated Cotton: Enhanced Insulation through PVA Nanofiber-Coated PCM Microcapsules
## 3 Results  
### Microcapsules Characterization  
Figure 2 presents an optical micrograph and a histogram detailing the size distribution of the microcapsules. The microcapsules appear as spherical entities with varying diameters, demonstrating the encapsulation process's effectiveness in producing uniformly shaped particles. The microcapsules have diameters ranging from 5 \(\upmu\)m to 24.5 \(\upmu\)m. By means of Image ] software, the total amount of microcapsules from the image in Figure 2 is 131; the most frequent size range is between 5.0 \(\upmu\)m and 6.0 \(\upmu\)m. This indicates that the majority of the microcapsules fall within this size range. There is a noticeable decreasing trend in frequency as the microcapsule diameter increases. Smaller microcapsules (5.0 \(\upmu\)m to 6.0 \(\upmu\)m) are more abundant, while larger microcapsules (24.0 \(\upmu\)m to 25.0 \(\upmu\)m) are much less frequent. Microcapsules were placed on the cotton fabric and SEM and FTIR analysis were conducted before the PVA nanofibers were used to coat them. Figure 3 illustrates the cotton fibers with some round spheres on them. Those round particles are attributed to the coco microcapsules. The FTIR spectra plot illustrates the absorbance spectrum for coco oil, ethylcellulose, cotton fabric, and cotton fabric with microcapsules (Figure 4). To identify the presence of microcapsules on the cotton fibers, we can look for new features in the microcapsules'spectrum (MC) which are distinct from cotton fabric (Co), but present in coco oil spectra (coco) and ethyl cellulose (EC). Figure 1: Scheme for the thermal measurement system. Figure 2: Microcapsule characterization. Histogram for microcapsules size distribution. Ethylcellulose presence can be demonstrated by the peak centered around 1046 cm. This peak is characteristic of ethylcellulose [18; 19] and clearly alters the spectrum for cotton fabric with microcapsules (MC). The prominence of this peak in EC and its presence in MC but not in coco oil or cotton indicates that the ethylcellulose component is a significant part of the MC material. It indicates that the microcapsules indeed contain ethylcellulose, likely forming the shell that encapsulates the core material (possibly coco oil in this case). Pure cotton (Co) does not typically show a strong absorption near 1707 cm\({}^{-1}\)[20], as cellulose does not contain carbonyl groups in its native form. The presence of a distinct peak at 1707 cm\({}^{-1}\) in the FTIR spectrum of the cotton fabric with microcapsules (MC), which is not present in the pure cotton (Co) fabric but is observed in both coco oil and ethylcellulose (EC), can indeed be indicative of the presence of microcapsules on the  
Figure 4: FTIR spectra for coco oil microcapsules on cotton fabric once the fabric has been heated for five cycles. Figure 3: SEM image for coco oil microcapsules on cotton fabric once the fabric has been heated for five cycles. Arrows indicate the microcapsules position. fabric. This peak likely corresponds to specific chemical functionalities associated with the microcapsules. The peak at around 1737 cm\({}^{-1}\) in the spectra of coco oil and ethylcellulose typically corresponds to C=O (carbonyl) stretching vibrations, which are common in ester or other carbonyl-containing groups [21; 22]. This is a characteristic peak for many organic compounds, especially those that contain ester groups, as in ethylcellulose. The shift from 1737 cm\({}^{-1}\) in coco and EC to 1707 cm\({}^{-1}\) in MC suggests a change in the chemical environment of the carbonyl group when the microcapsules are formed and applied to the cotton fabric. The interaction between the coco oil and the ethylcellulose may alter the electronic environment around the carbonyl groups, leading to a shift in the absorption frequency. It might indicate the formation of new chemical bonds or interactions, such as hydrogen bonding, due to the encapsulation process, that affect the carbonyl group's vibration frequency [20; 21; 22].