## 3 Results and Discussion  
The structure of monomers2a-2f and PAI3a-PAI3f films were confirmed by IR and \({}^{1}\)H NMR spectra. The elemental analysis values of the polymers agreed well with the calculated values for the expected structures. (Figures S1-S4). The thermal stability of PAI films was investigated through TGA and DSC. The TGA and DSC measurements of PAI3a-3f were explored, as shown in Figures S5 and S6, respectively. The glasstransition temperature (Tg) obtained from DSC and the temperatures corresponding to a weight loss of 5% (T5) and 10% (T10) of PAIs acquired from TGA are summarized in Table 1. The temperatures of initial decomposition (T5 and T10) which ranged from 296 \({}^{\circ}\)C to 323 \({}^{\circ}\)C and from 323 \({}^{\circ}\)C to 390 \({}^{\circ}\)C, respectively, and the high char yields (46.15-58.67%) at 800 \({}^{\circ}\)C of PAI3a-3f showed good thermal stabilities of these polymers. Compared to PAI3f, PAI3a show a higher Tg value, which indicates that the PAIs with the L configuration have better thermal properties than those with the D configuration. In fact, we also investigated PAIs containing the other differential configurations of amino acids such as phenylalanine, leucine, etc. The PAIs with L configuration also have a higher Tg value. This may be the cause of natural selection. All these PAIs, except for the PAI3f, have the same polymer backbone, but have differential side groups based on differential amino acids. PAI3a and PAI3e have Tg values greater than PAI3b. The volume effect of the side group played a leading role, resulting in a higher Tg values for PAI3a and PAI3e. Among them, the side groups of PAI3a and PAI3e are all normal paraffin chains. The side groups of PAI3e have greater length and flexibility, resulting in internal plasticization. This makes the Tg value of PAI3e smaller than PAI3a. Through the comparison of PAI3b and PAI3c, a lower Tg value is attached to PAI3c. This may be due to the fact that the isolation effect dominated at the time, because the volume of the isopropyl group was much bigger than that of the methyl group. This increased the distance between the main chains and made it less likely to form hydrogen bonds, and also weakened the intermolecular forces. Therefore, PAI3c has the lowest Tg value. However, due to the combined effect of volume effect and isolation effect, PAI3d has a Tg value slightly lower than PAI3b and significantly higher than PAI3c. On one hand, in the polymer we synthesized, the L configuration and the D configuration of the amino acid affected the Tg values. On the other hand, when the main chain is the same, the volume effect of the side groups, the internal plasticizing effect and the isolation effect also had an effect on the Tg values. Figure 1 shows the change in molecular weight at different stages of enzymatic degradation. As the degradation time prolongs, the molecular weight gradually decreases. This illustrates the loss of small molecules during the degradation process. As can be seen in Figure 1, the fastest degradation rate of PAI3b is up to 50%, PAI3e is the slowest degradation, and molecular weight loss is less than 10%. Although glycine has no chirality, PAI3b degrades faster than PAI3a. This indicates that the structure of amino acids has the greatest influence on the degradation performance of PAI relative to chirality. From PAI3a to PAI3c to PAI3d, the degradation rate gradually slows down. This indicates that for natural chiral amino acids, the rate of degradation decreases as the carbon chain grows. This may be because the hydrophilicity of polymers decreases with the increase of side-group carbon chains. The microorganisms in nature are all hydrophilic, so the longer the carbon chain of the side group, the more difficult it is to be degraded. PAI3e is an unnatural amino acid. Although its side-group carbon chains are shorter than the PAI3d, its degradation rate is the lowest.