Comparison of Eco-friendly Ti–M Bimetallic Coordination Catalysts and Commercial Monometallic Sb- or Ti-Based Catalysts for the Synthesis of Poly(ethylene-co-isosorbide terephthalate)

[Image: see text] Sustainable development greatly benefits from the effective synthesis of bio-based copolymers that are environmentally friendly. To enhance the polymerization reactivity for the production of poly(ethylene-co-isosorbide terephthalate) (PEIT), five highly active Ti–M (M = Mg, Zn, Al, Fe, and Cu) bimetallic coordination catalysts were designed. The catalytic activity of Ti–M bimetallic coordination catalysts and single Sb- or Ti-based catalysts was compared, and the effects of catalysts with a different type of coordination metal (Mg, Zn, Al, Fe, and Cu) on the thermodynamic and crystallization properties of copolyesters were explored. In polymerization, it was found that Ti–M bimetallic catalysts with 5 ppm (Ti) had higher catalytic activity than traditional antimony-based catalysts or Ti-based catalysts with 200 ppm (Sb) or 5 ppm (Ti). The Ti–Al coordination catalyst showed the best-improved reaction rate of isosorbide among the five transition metals used. Utilizing Ti–M bimetallic catalysts, a high-quality PEIT was successfully synthesized with the highest number-average molecular weight of 2.82 × 10(4) g/mol and the narrowest molecular weight distribution index of 1.43. The glass-transition temperature of PEIT reached 88.3 °C, allowing the copolyesters to be used in applications requiring a higher T(g), like hot filling. The crystallization kinetics of copolyesters prepared by some Ti–M catalysts was faster than that of copolyesters prepared by conventional titanium catalysts.