Novel biobased poly(hexamethylene-co-diethylene glycol furandicarboxylate) copolyesters with improved mechanical properties and hydrolytic degradation rates

Abstract

Poly(hexamethylene 2,5-furandicarboxylate) (PHF) is a promising biobased polyester with excellent thermal, mechanical, and barrier properties. In this research, a series of high molecular weight biobased poly(hexamethylene-co-diethylene glycol furandicarboxylate) (PHDEGF) copolyesters were successfully synthesized using a two-step melt polycondensation method to improve their mechanical and hydrolytic degradation properties and extend their practical application. The thermal properties, crystal structures, mechanical properties, and hydrolytic degradation of PHDEGF copolyesters were investigated in detail and compared with those of PHF. PHDEGF copolyesters were random as shown by ¹³C NMR spectroscopy. On increasing the diethylene glycol furandicarboxylate (DEGF) unit content, the glass transition temperature of PHDEGF gradually increased while the melting point decreased or even disappeared at a high DEGF unit content. The elongation at break of PHDEGF copolyesters with about 20 to 65 mol% of DEGF units was significantly higher than that of PHF. PHDEGF30 containing about 20 mol% of the DEGF unit displayed comparable or even superior mechanical properties to those of commercial poly(butylene adipate-co-terephthalate) and poly(butylene succinate). In addition, the hydrolytic degradation behavior of PHF and PHDEGF was studied in a NaOH solution (pH = 14, 37 °C). The incorporation of the DEGF unit significantly accelerated the hydrolytic degradation of PHDEGF copolyesters.