*3.1. Materials*

PLA (4032D) and SG were commercially obtained from Nature Work Company (Blair, NE, USA) and Ningbo Global Biomaterials Co., Ltd. (Ningbo, China), respectively. APP (analytical reagent) (AR) and DOPO (AR) were purchased from Sigma-Aldrich (Saint Louis, MO, USA). EA (AR), 4-dimethylaminopyridine (4DMAP) (AR), xylene (AR), chloroform (AR), anhydrous ethanol (AR) and N, N-Dimethylformamide (DMF) (AR), were supplied by Aladdin Industrial Co. (Beijing, China). All reagents were used without any further purification.
