The chemical structure of furan-based copolymers was also validated by ATR-FTIR analysis (Fig. There are two potential explanations for this phenomenon. Firstly, diols with longer alkylene chains have increased enzymatic reactivity, leading to the production of polyesters with higher degrees of polymerization. Secondly, it was proven that the solubility of the furanic-aliphatic polyesters decreases while using α,ω-ALD with shorter chains. Additionally, different melting temperatures (Tm) of copolyesters were noticed. PHF-DLF/POF-DLF materials are characterized by higher Tm (130 and 127 °C, respectively) than that of PDF-DLF/PDDF-DLF materials (96 and 92 °C, respectively) (Table ), as well as by the synthesis temperature applied during the I and II stage (95 °C). Therefore, during the reaction of DMFDCA with 1,6-HDO/1,8-ODO, low molecular weight products could be precipitated from the reaction media due to their high Tm, until the temperature was raised to 140 °C in the final III temperature stage. As a result, polymerization efficiency was lower since CAL-B was unable to reach the polymers most of the reaction time, hence, lower molecular weight values were obtained. On the other hand, enzymatic polymerization of DMFDCA with 1,10-DDO/1,12-DDDO diols which exhibits lower Tm (95 and 91 °C, respectively) proceeded constantly with the same efficiency since no product precipitated out from the reaction media, and the access of CAL-B to polymers was not hindered. As a result, high-molecular-weight copolymers were obtained.