## 3 Results and Discussion
The XPS spectra in the C 1s region (Figure 2a) for poly(S-MVT) reveal that the C 1s band can be deconvoluted into four peaks at 284.4, 284.9, 285.4, and 286.3 eV, which could be attributed to C=C/C-C bonds, C-N bonds, C-S bonds, and C=N bonds, respectively. In the S 2p spectrum of the poly(S-MVT) (Figure 2b), the peaks at 161.8 eV and 164.2 eV are due to the HS\({}_{\circ}\)C [30] and C-S-S, respectively. The two peaks at 163.6 and 165.0 eV arise from the C-S-C [26]. This further confirmed the sulfur species have successfully linked to the thiazole molecules. The high-resolution N 1s XPS spectrum of poly(S-MVT) (Figure 2c) can be deconvoluted into two peaks at 398.7 and 400.1 eV, corresponding to C=N-C, and C-NH\({}^{+}\)[26; 31], respectively. The appearance of N 1 s peak at 400.1 eV further confirmed that some nitrogen atoms are protonated, i.e., the tertiary nitrogen atom of thiazole ring forms a salt with the H proton, and the H proton may be originated from the SH. This means that there may be a moiety as illustrated in Figure 2d existing in the poly(S-MVT). This structure could facilitate the electrochemical reaction rate when used as a cathode material [31; 32; 33]. XRD is one of the most efficient measurements to analyze elemental sulfur in the sulfur polymers based on S\({}_{8}\). As Figure 3a shows, the transformation of crystalline state intuitively demonstrated the involvement in the polymer. Irrespective of the content of MVT, the diffraction peaks of crystal sulfur are extremely weak and even disappeared when the MVT content is over 15%. Moreover, new XRD peaks that are not present in the elemental sulfur appear in the poly(S-MVT)s, and the peak positions are concentrated in the range of 19.2-20.7\({}^{\circ}\) and 23.4-24.2\({}^{\circ}\), demonstrating the elemental sulfur is almost fully polymerized in the polymer. Thermal analysis was also conducted on the poly(S-MVT) with varying MVT content to further confirm the formation of the copolymer. DSC revealed that poly(S-MVT)s with compositions that ranged from 10 to 50% MVT exhibited glass transition temperature (Tg) values from \(-\)27.7 \({}^{\circ}\)C to 9.4 \({}^{\circ}\)C, and the Tg values increase with MVT content progressively (Figure 3b). MALDI-TOF MS spectrum (Figure S7) showed that  
Figure 1: (**a**) FTIR spectra of MVT and Poly(S-MVT) (50% MVT); (**b**) HNMR spectra of poly(S-MVT) (15% MVT). the molecular weight of the polymer was less than 1600 and concentrated in 568, which indicated that the low glass transition temperature and good solubility of the copolymers might be due to the low molecular weight. The morphologies and structures of the poly(S-MVT)s were examined by SEM and TEM measurements. As shown in Figure 4, all the poly(S-MVT)s had abundant pores on the external surface. This meso/macroporous structure was further confirmed by TEM (Figure 5a,b). The high TEM magnification image (Figure 5b) clearly showed that the pore diameters of poly(S-MVT) (15% MVT) were in the range of 30 to 300 nm. Furthermore, high-resolution elemental mapping analysis of a selected area (Figure 5c) indicates that C, N, and S elements are distributed uniformly throughout the entire poly(S-MVT) (Figure 5d-f). This merit is a benefit for enhanced fast ionic conduction and mass transportation when used in cathode of a Li-S battery. Moreover, the porous structure can help suppress the  
Figure 3: (**a**) XRD patterns of poly(S-MVT)s with different MVT content. (**b**) DSC thermograms of poly(S-MVT)s (second scan) with different MVT content. Figure 2: High-resolution (**a**) C1s, (**b**) S2p, and (**c**) N1s XPS spectra of poly(S-MVT) (15% MVT). The black curves are the experimental data, and the colored curves are deconvolution fits. (**d**) Proposed partial structure of protonated poly(S-MVT). volume expansion of active sulfur during charging and discharging process [34; 35]. The formation mechanism of the porous structure is not clear and needs further study.