4. Conclusions In this study, a series of hydrophilic PBT with different molecular weights were synthesized, and used to chemically modify theCS by the coupling reaction between carboxyl groups on PBT chain and amino groups on CS mediated by EDC, while aqueous solution of BSMIM·CF3SO3 was chosen as the green solvent. The chain length of grafted PBT could be facilely controlled. 1H NMR, and ATR-FTIR spectra confirmed that the aliphatic polyester has been successfully grafted onto CS. The T g of the copolymer approached steadily to the Tgof pure PBT with increasing molecular weight of PBT. Mean-while, WAXD analysis suggested that the crystallinity of CS reduce dobviously after grafting with PBT. The CS-g-PBT copolymers exhibited good solubility in deionized water.