## 3 Results and Discussion  
In this study, the researchers used the one-shot solvent-free bulk polymerization method to synthesize polyol, MDI, and BDO into TPU. Because 1,3-BDO was used in place of 1,4-BDO as a chain extender, FT-IR analysis had to be used to confirm any changes in the structure of the TPUs. FT-IR spectrum diagrams of TPUs with three different functional groups are displayed in Figure 1. A stretching and bended vibration-NH absorption band is present at the 3330 cm\({}^{-1}\) point; this is a characteristic of a carbamate functional group. The vibration band present at the 2730 cm\({}^{-1}\) point has a N=C=O structure; these representations of absorption peaks also indicate a carbamate functional group. These results indicate that TPU was successfully synthesized using both 1,3-BDO and 1,4-BDO as the chain extender with varying polyols. The number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI), according to the molecular distribution data obtained from the GPC analysis, are listed in Table 3. The results revealed that even when 1,4-BDO was replaced by 1,3-BDO, TPU with high molecular weight could be polymerized. The PDI values of all the TPU samples were lower than 2.0; this means that this method is applicable in terms of polymer processing (e.g., injection molding and extrusion) [13]. Next, thermal analysis and testing were conducted to confirm the structure. Examination of the thermal properties was performed to gain further understanding of the TPUs for application and research. TGA was used to evaluate thermal stability during the thermal degradation process. Figure 2 illustrates the thermal degradation conditions of TPU under inert gas; the figure indicates that even when different chain extenders were used during the polymerization process, the thermal degradation temperatures of the TPUs were similar (approximately 300 \({}^{\circ}\)C). For PBA and PTMG groups, the TGA spectra indicate a two-stage thermal degradation [58], and this involves the degradation of the hard and the soft chain segments [59]. The first stage of degradation is related to carbonate bonds, whereas the second stage  
Figure 1: Fourier transform infrared (FT-IR) light spectrum diagram of the three groups of TPU, synthesized using different polyols (PBA, PTMG, or PCDL) and different chain extenders. (**a**) full graph and (**b**) graph between 2500 to 3500 cm\({}^{-1}\). (the arrow is located in 3300 cm\({}^{-1}\)). \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Polymer Code**} & **Mn** & **Mw** & **Mw/Mn** \\  & **(g/mol)** & **(g/mol)** & **(PDI)** \\ \hline PBA-1,3-R = 1 & 106,553 & 160,281 & 1.50 \\ PBA-1,3-R = 1.02 & 109,180 & 184,483 & 1.69 \\ PBA-1,4-R = 1 & 153,223 & 274,070 & 1.79 \\ PBA-1,4-R = 1.02 & 141,036 & 208,916 & 1.48 \\ PCDL-1,3-R = 1 & 126,288 & 198,902 & 1.58 \\ PCDL-1,3-R = 1.02 & 82,993 & 150,089 & 1.81 \\ PCDL-1,4-R = 1 & 187,687 & 356,779 & 1.90 \\ PCDL-1,4-R = 1.02 & 94,794 & 151,253 & 1.60 \\ PTMG-1,3-R = 1 & 114,117 & 163,701 & 1.43 \\ PTMG-1,3-R = 1.02 & 108,948 & 162,242 & 1.49 \\ PTMG-1,4-R = 1 & 96,633 & 142,240 & 1.47 \\ PTMG-1,4-R = 1.02 & 109,293 & 183,788 & 1.68 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) of the TPUs synthesized in this study. originates from the polyol structure. However, only one peak was observed for the PCDL group; this is probably because the PCDL group has a higher level of phase mixture; thus, the two-stage degradation is less obvious [60]. With regard to the degradation temperature (T\({}_{\text{d}}\)), when the weight loss was 5%, the Td of the TPU polymerized using 1,3-BDO was 2-5 \({}^{\circ}\)C lower than the Td of the TPU polymerized using 1,4-BDO. The reason behind this is probably that the methyl bonds of 1,3-BDO can be damaged more easily under high temperature, and this resulted in a relatively lower thermal degradation temperature.