Bio-Based Aromatic Polyesters with Tunable Thermomechanical Properties, Wettability, UV Shielding, and Enzymatic Degradability: Effect of Diol Symmetry.

A diol symmetry-driven strategy was employed, tailoring the performance and end-of-life of bio-based aromatic copolyesters. A series of random copolyesters, BHB-PDn and BHB-HDn (n = 1-2.5), were synthesized via melt polycondensation of BHBB (diol) and BHMB (diester) with asymmetric 1,3-propanediol (PD) or symmetric 1,6-hexanediol (HD). Symmetric HD promoted semicrystalline domains (18-25%), yielding higher Tg (85.7-67.8 °C), tensile modulus (1.93-1.79 GPa), yield strength (65.7-47.5 MPa), and hydrophobicity (WCA 88.6-80.3°). In contrast, asymmetric PD produced predominantly amorphous domains (low crystallinity 8-15%) with enhanced ductility (εb 175-250%) and lower Tg (66.5-53.6 °C). Both series displayed excellent UV shielding (Tav-UVA < 4.7%, T400 nm <10%), significantly surpassing PET. Under enzymatic conditions with Thc_Cut1 cutinase (50 °C, 120 days), BHB-PD1.0 and BHB-HD1.0 achieved 35.5% and 30.8% weight loss, respectively, 4-fold higher than PET (<2%). This symmetry-controlled strategy offers a versatile pathway for next-generation sustainable polymers.