Biodegradable Copolyesters with Unexpected Highly Blocky Microstructures and Enhanced Thermal Properties

To synthesize novel biodegradable polyesters with high heat resistance and good crystallization capability, we designed a series of aliphatic-aromatic copolyesters, i.e., poly(isoidide-2,5-dimethylene adipate-co-terephthalate)s (PIATs) based on isoidide-2,5-dimethanol (IIDML), a rigid carbohydrate-based building block. The Mn values and intrinsic viscosities of PIAT copolyesters containing up to 40 mol % aromatic moieties are in the range of 6 000–19 000 g·mol–1 and 0.5–0.87 dL·g–1, respectively. Interestingly, the products were obtained as blocky copolymers after the one-pot melt polycondensation process because of the thermodynamic equilibrium of IIDML moieties driven by the insufficient thermal stability of the IIDML moieties. In addition, all the copolyesters are semicrystalline with crystallinity from 28% to 55% and tunable Tm values ranging from 88 °C to a remarkable 189 °C. They exhibit better (bio)degradability than the same type of polyesters. This work shows that this green monomer plays a key role in balancing thermal properties (especially Tg) and (bio)degradability, and these polyesters potentially broaden the application toward, for example, fibers.