Tricyclic Diester and 2,5-Furandicarboxylic Acid for the Synthesis of Biobased Hydrolysis Copolyesters with High Glass Transition Temperatures

The reluctance of a polyester with high glass transition temperature (T_g) and mechanical properties to hydrolyze is a well-known fact, for instance, the high hydrolysis resistance of aromatic polyesters based on terephthalic acid and 2,5-furandicarboxylic acid (FDCA). The synthesis of polyesters that have a high T_g (>100 °C) and a fast hydrolytic degradation quality at the same time is a valuable topic. Herein, a renewable rigid diester, N,N'-trans-1,4-cyclohexane-bis(pyrrolidone-4-methyl carboxylate) (CBPC), was obtained via Michael addition. CBPC was copolymerized with FDCA and ethylene glycol to prepare a series of copolyesters PECxEFy with a high M_n over 30 kDa. PECxEFy showed a T_g range of 75.2-109.2 °C which outdistanced the most biobased polyesters. The thermal stability of all PECxEFy remained unchanged with the introduction of CBPC. Moreover, PECxEFy presented superior mechanical performances which were matching or exceeding those of commercial polyethylene terephthalate (PET) and polylactic acid (PLA). PECxEFy was stable in air but was able to undergo noticeable hydrolytic degradation, proving their enhanced degradability. And the regulation between CBPC and FDCA composition can be leveraged to adjust the degradation and environmental durability of PECxEFy, up to practical applications. Computational studies systematically revealed the relationship between CBPC with a tricyclic structure and the improved T_g and hydrolyzation properties. The outstanding thermal and mechanical performances and hydrolysis of these copolyesters appear to be promising candidates for renewable alternatives to industrial petrochemical polyesters.