## 3 Results and Discussion
### The Effect of the BA/BI Ratio of PBABA Copolymers with an EDTA Concentration of 0.1 mole%
The \(M_{\mathrm{w}}\) had more significant values from 29,280 to 178,838 g-mole\({}^{-1}\), implying that the PBABI copolyesters had more massive globule structures because they could form partial cross-linking networks via the EDTA. The polydispersion index (PDI) ranged from 1.754 to 7.123, due to the more massive \(M_{\mathrm{w}}\), resulting from a partially cross-linked structure forming the network architecture. For the thermal behavior, the first cycle Figure 3a heating and Figure 3b cooling curve, and second cycle Figure 3c heating curve was run in DSC so that the crystallization in PBABI copolyesters could be observed during the cooling procedures, and the melting behavior could be seen in the subsequent reheating at 10 \({}^{\circ}\)C-min\({}^{-1}\). The \(T_{\mathrm{m}}\) decreased as IA concentration increased. Furthermore, the \(T_{\mathrm{m}}\) peaks tended to separate into two peaks with IA concentrations above 20 mole%, in both the first and second cycle heating procedures, suggesting that AA and IA might form separate packing routines. \begin{table}
\begin{tabular}{l c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Item**} & **Feed** & **Calculated** & \multirow{2}{*}{**H1**} & \multirow{2}{*}{**H2**} & \multirow{2}{*}{**H3**} & \multirow{2}{*}{**H4**} & \multirow{2}{*}{**H5**} & \multirow{2}{*}{**H6**} & \multirow{2}{*}{**H7**} & \multirow{2}{*}{**H8**} \\  & **Ratio** & & & & & & & & & \\ \hline BA/BI = 10/0 & 0 & 0 & 1.838 & 1.929 & 2.015 & 2.605 & & 4.361 & & \\  & & & (1.004) & (0.992) & (0.028) & (1.000) & & (1.001) & & \\ BA/BI = 9/1 & 10 & 4.51 & 2.169 & 2.231 & 2.545 & 2.922 & 3.948 & 4.675 & 6.343 & 6.942 \\  & & & (0.997) & (0.992) & (0.015) & (1.000) & (0.031) & (1.024) & (0.02) & (0.02) \\ BA/BI = 8/2 & 20 & 11.41 & 2.015 & 2.101 & 2.408 & 2.793 & 3.794 & 4.547 & 6.224 & 6.814 \\  & & & (0.983) & (0.828) & (0.019) & (1.000) & (0.091) & (1.039) & (0.039) & (0.052) \\ BA/BI = 7/3 & 30 & 15.01 & 1.841 & 1.923 & 2.237 & 2.579 & 3.632 & 4.376 & 6.044 & 6.626 \\  & & & (1.000) & (0.944) & (0.02) & (1.000) & (0.125) & (1.101) & (0.075) & (0.047) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The composition of the C=C bond of itaconic acid within PBABI copolyesters, chemical shifts (ppm), and the integral ratio (the value in brackets) of \({}^{1}\)H NMR spectra for PBABI copolyesters. Figure 2: FT-IR spectra of the PBABI copolyesters. Figure 3: Differential Scanning Calorimetry (DSC) trace of the PBABI copolyesters. (**a**) Heating curves in the first cycle, (**b**) cooling curves in the first cycle, and (**c**) heating curves in the second cycle. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \begin{tabular}{c} **\(\boldsymbol{M_{\mathrm{n}}}\)** \\ **(d-lg\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} \(\boldsymbol{M_{\mathrm{n}}}\)** \\ **(g-mole\({}^{-1}\))** \\ \end{tabular} & \
\begin{tabular}{c} \(\boldsymbol{M_{\mathrm{w}}}\)** \\ **(g-mole\({}^{-1}\))** \\ \end{tabular} &
\begin{tabular}{c} \(\boldsymbol{M_{\mathrm{w}}}\)** \\ **(PDD)** \\ \end{tabular} \\ \hline BA/BI = 10/0 & 0.98 & 16,696 & 29,280 & 1.754 \\ BA/BI = 9/1 & 1.02 & 35,171 & 89,571 & 2.547 \\ BA/BI = 8/2 & 1.14 & 28,323 & 113,520 & 4.008 \\ BA/BI = 7/3 & 1.22 & 25,108 & 178,638 & 7.123 \\ \hline \end{tabular}
\end{table} 
Table 2: Intrinsic viscosity (I.V), \(M_{\mathrm{n}}\), \(M_{\mathrm{w}}\), and \(M_{\mathrm{w}}\)/\(M_{\mathrm{n}}\) of gel permeation chromatography with hexafluoroisopropanol (HFIP) as the solvent for the PBABI copolyesters. Competition for reactivity with 1,_A_-BDO was also observed in the copolymerization reaction. The \(\Delta H_{\rm m}\) decreased as IA increased, but the highest \(\Delta H_{\rm m}\) of the PBABI copolyesters was obtained at BA/BI = 9/1, at a value of 60.3 mJ\(\cdot\)mg\({}^{-1}\), caused by the more considerable molecular weight, to assist the molecular chain in packing well, into the crystal region.