Renewable and Biodegradable Tetrahydrofuran-Based Polyester Amides

Polyamides are high-performance engineering materials but are generally not biodegradable. In contrast, aliphatic polyesters are prone to biodegradation but exhibit relatively low melting points and limited mechanical strength. Polyester amides unite the susceptibility of biodegradation of aliphatic polyesters with the excellent thermal and mechanical performances of polyamides. This work covers the synthesis of a series of renewable polyester amides based on nylon-6,6 salt, adipic acid, and 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF). BHMTHF, also known as 2,5-tetrahydrofurandimethanol (THFDM), is a rigid alicyclic structure derived from HMF. The incorporation of BHMTHF reduces the crystallinity and mobility of (co)polymers. The polyester amides were produced via a straightforward bulk polymerization process, which resulted in high Mn¯ (23,200–30,600 g/mol) statistically random copolymers in a relatively short reaction time (8 h). A higher amide content increased the Tg (−26 to −6 °C) and Tm (90 to 197 °C) values and the degree of crystallinity. In terms of mechanical performance, a higher amide content improved the tensile strength and E-modulus, whereas the elongation at break decreased. Water contact angle experiments confirmed the hydrophilic character of the synthesized polyester amides. Finally, biodegradation experiments in activated sludge demonstrated that all polyester amides are prone to biodegradation. These biobased polyester amides possess a unique combination of good thermal and mechanical properties in combination with biodegradability. This is accompanied by a facile and industrially preferred synthesis process and tunable properties via straightforward alteration of the amide content.