Study on Synthesis and Properties of Oxybis Benzoic Aromatic Polyesters

A series of oxybis benzoic aromatic polyesters were prepared by a two-step polymerization method of esterification and polycondensation, using 4,4'-oxybis(benzoic acid) (OBBA) and aliphatic diols with different carbon chain lengths (C2-8) as monomers, and tetrabutyl titanate (TBT) as catalyst. The results showed that the M_n of the prepared polyester was between 25350–42040 g/mol, and the polymer dispersity index (PDI) was about 2.0. The results of DSC, WAXD and UV–Visible spectroscopy showed that polyethylene oxybisbenzoic (PEO), polypropylene oxybisbenzoic (PPO), polybutylene oxybisbenzoic (PBO), polypentene oxybisbenzoic (PPeO) and polyhexene oxybisbenzoic (PHO) polyesters were amorphous, and the transmittance at 550 nm (T₅₅₀) were 75.0–85.2%, showing good light transmittance. The crystallization rate of polyheptylene oxybisbenzoic (PHeO) and polyoctylene oxybisbenzoic (POO) was slow, which changed from amorphous to semi-crystalline after been placed at room temperature for 10 days, resulting in no transparency. With the increase of carbon chain number of diols in polyester, the T_g of polyesters decreased gradually. TGA test results showed that PEO polyester had higher thermal stability (T_5% = 407.8°C, T_d = 441.9°C). The Young’s modulus and tensile strength of the polyester gradually decreased with the increase of the number of diol carbon chains. The elongation at break of polyesters with odd carbon chain diols was low (<20%), while the elongation at break of polyester with even carbon chain diols gradually increased from 4.2 to 1230.2%, which changed from brittle material to ductile material. The rheological properties analysis showed that the aromatic polyesters were typical pseudoplastic fluids.