Synthesis of a high-performance citric acid-based polyester elastomer by a hot-pressing technique

The high-performance bio-based elastomer, poly (1, 4-cyclohexanedimethanol succinate-co-citrate) (PCSC), was successfully synthesized through the combination of melt polymerization and hot pressing. Owing to the structural characteristics of citric acid (CA), an effective process of thermal- and pressure-integrated crosslinking was possible, revealing CA to be a progressive tetra-functional monomer. In the composition of PCSC, there can be four types of ester bonds amongst monomers, of which CA was used in three. Specifically, the stepwise hot-pressing method allowed β-carboxylic acid and hydroxyl group of CA to remain within the synthesized elastomer to enhance its crosslinking density via esterification. As a result, the synthesized PCSC possessed a wide range of mechanical properties along with good thermal resistance. The resulting characteristics were demonstrated by fourier-transform infrared spectroscopy (FT-IR), two-dimensional correlation spectroscopy (2D-COS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile and swelling tests. PCSC is a sustainable and versatile material that can be utilized in the field of engineering.