Synthesis and degradability of copolyesters of 2, 5-furandicarboxylic acid, lactic acid, and ethylene glycol

Polyethylene 2, 5-furandicarboxylate-lactic acid copolyesters (PEFL) were synthesized from bis (hydroxyethyl)-2, 5-furandicarboxylate and oligomer of l-lactic acid, through two-stage condensation. The polyesters were characterized using FTIR, 1H NMR, GPC, and WXRD. The weight-average molecular weight (Mw) of the polyesters ranged from 68240 to 130433. The glass transition temperature (Tg) of the copolyesters increased gradually with increasing content of 2, 5-furandicarboxylate. In phosphate buffer solution (PBS, pH = 7.4) and in soil, the degradability of the polyesters was evaluated for 55 d. More weight loss was obtained with a higher ratio of lactate polymers in soil than those with a lower ratio in PBS. After 55 d, the weight loss of PEFL20/80 reached 65% and 24% in soil and PBS, respectively. However, the mole fraction of lactyl and furanic units that was calculated by 1H NMR data did not change. Comparing the scanning electron microscopy images, we found many micro-cracks on the copolyester surfaces. Meanwhile, Mw and Tg also decreased prominently during degradation.