Modulating Crystallization Behavior to Improve Melt Processability and Mechanical Performance in PCT Copolyesters via Benzenedimethanol Incorporation

Abstract

Poly(1,4-cyclohexanedimethylene terephthalate) (PCT) suffers from a narrow melt-processing window and low elongation at break, limiting manufacturability and toughness. Rigid 1,4-benzenedimethanol (BDM) was incorporated via melt polycondensation, followed by solid-state polymerization to increase molar mass, and poly(1,4-benzenedimethanol-co-1,4-cyclohexanedimethylene terephthalate) (PBCT) copolyesters with tunable compositions were prepared. FT-IR, 1H NMR, and 13C NMR confirmed the random copolymer structures. BDM reduced the melting temperature and suppressed crystallization, broadening the processing window, and improved the ductility. PB17CT exhibited 142% elongation at break and 48 MPa tensile strength. Rheological measurements indicated stable chain entanglement and melt integrity. These results demonstrate that the synergy between rigid and flexible segments simultaneously regulates crystallization and mechanical performance, providing a molecular-level strategy for designing semicrystalline copolyesters with balanced processability and toughness.