Bio-based poly(neopentyl glycol succinate-co-isosorbide succinate) copolymers: synthesis, kinetics of thermal decomposition and degradation in different water

In order to design novel bio-based and water-degradable polyesters with high heat resistance and good mechanical properties, we synthesized a series of poly(neopentyl glycol succinate-co-isosorbide succinate) (PNSI)-based isosorbide building blocks via melt polycondensation. The molar content of isosorbide succinate ranged from 20 to 70%. The kinetics of thermal decomposition showed that with an increase in the isosorbide molar content, the degradation activation energy (E_a) of the copolyesters significantly increased. From Kissinger and Flynn–Wall–Ozawa models, the E_a of PNSI copolymer with 40% molar content of isosorbide succinate segment content was 92.7 and 104.5 kJ mol⁻¹, respectively, which was higher than PNS copolymers (69.1 kJ mol⁻¹ and 87.7 kJ mol⁻¹). In addition, the isosorbide structure containing hydrophilic ether bonds increased the degradation rate of polyester. The weight loss of the PNSI40 copolymer was greater than 89% after 42 days of degradation in an alkaline solution. This study showed that the bio-based monomer isosorbide could balance thermal properties (especially T_g) and water/biodegradability. In addition, the copolymer is nontoxic; thus, the PNSI copolymer is an ideal membrane material with a wide range of packaging applications.