Synthesis of Polyester Copolymers via Two-Stage Melt Polymerization

The synthesis was carried out using two different melting stages with different levels of vacuum (Figure 1). It was conducted by dosing calculated amounts of materials based on 1 mole of dicarboxylic acid. The first melting stage was the esterification stage, the second was the polycondensation stage. The esterification progressed at approximately 200–210 °C. The theoretical amount of by-products was obtained through esterification against dimethyl terephthalate and 1,4-butanediol with the 0.75 (g/mole) TBT catalyst and sebacic acid was added to the second esterification reaction against oligomer (T-B). The esterification was finished after obtaining the theoretical amount of calculated by-products. After esterification, we initiated polycondensation by increasing the temperature to 240 °C and decreasing the vacuum level (1.5 torr). All experiments were conducted using different molar ratios of sebacic acid and dimethyl terephthalate; the ratio of 1,4-butanediol to dicarboxylic acid was fixed as 1.25:1 mol/mol.