Synthesis of Citric Acid-Derived Tricarbonate (CA-TC) Resins and Properties of the Cured Resins

Abstract

Citric acid-derived trifunctional 5-membered cyclic carbonate (CA-TC) resins were synthesized by allylation, epoxidation, and carbon dioxide insertion to three carboxy groups of a citric acid. The resins were thermally cured with trioxyethylene diamine (TODA), and cured CA-TC/TODA films were prepared. Thermal properties of the cured material were examined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The glass transition temperature (T_g) and 5% weight loss temperature (T_d5) of the cured CA-TC/TODA were determined to be -23.8℃ and 223℃, respectively. These results indicated that the cured material was rubbery at room temperature and easily decomposable at elevated temperature. By tensile testing of the cured film, we found the tensile modulus, tensile strength, and elongation at break were 0.46 MPa, 0.26 MPa, and 0.68, respectively, which shows that the cured material was soft and flexible. Examination of the enzymatic degradation of the cured materials revealed their high degradability by lipase from porcine pancreas and protease from streptomyces griseus.