It can be discovered that the molecular weight of PBT obtained was larger than 1000 and high enough for the subsequent grafting experiment. Also, the molecular weight increased regularly from 1000 to 2500 with the increase of reaction temperature from 80◦C to 120◦C due to the increasing reaction rate. Therefore, it can be concluded that the reaction process was simple and feasible to yield polyesters with Mn higher than 1.0 × 103. The PBT1–4 samples were totally soluble in water due to the presence of hydrophilic pendant hydroxyl groups on the polymer chain. How-ever, the PBT 5 was partially soluble in DMF or DMSO because of the crosslinked structure, suggesting the occurrence of the reaction between pendant hydroxyl and carboxyl group at 150◦C. Thus, there action temperature should be lower than 150◦C for the synthesis of linear PBT.