Synthesis of high-Tg fluorinated polyesters based on 2,5-furandicarboxylic acid

Abstract

The polyesters derived from renewable resources with both high transparency and good heat resistance are urgently desirable. Destroying the crystallization of a material and achieving an amorphous state can ensure high transparency, while good heat resistance can be provided by rigid monomers. Herein, the fluorinated rigid diol 2,3,5,6-tetrafluoro-1,4-benzenedimethanol (TFBDO) was introduced into 2,5-furandicarboxylic acid (FDCA)-based copolyesters to synthesize a series of new bio-based polymers called poly(ethylene-1,4-cyclohexyldimethylene-2,3,5,6-tetrafluoro-1,4-benzenedimethanol 2,5-furandicarboxylate) (PECFF) with different TFBDO contents via a two-step melt polycondensation. The number average molecular weight (Mn) of 24,200 ∼ 46,700 g/mol and the polydispersity index (PDI) of 1.28 ∼ 1.74 for synthesized PECFFs showed the high reaction activity as a rigid diol of TFBDO. As the increasing of tetrafluoro-1,4-benzenedimethanol unit, the Tg was improved from 91 °C for PECFF-15 to 118 °C for PECFF-75, and the thermal stability of Td,5% in nitrogen increased from 371 to 393 °C as well as the hydrophobicity, and gas barrier properties were also improved. When the content of the tetrafluoro-1,4-benzenedimethanol unit was up to 60 %, the copolyester PECFF-60 exhibited the Tg of 113 °C, Td,5% of 421 °C, Young’s modulus of 2460 MPa, and tensile strength of 71 MPa. Moreover, the surface water contact angle increased from 85° to 101° as well as the CO2 and O2 barrier properties improved 43.3-fold and 8.6-fold compared with PET. These studies have shown that the new bio-based polyester could be a potential application in many fields, such as transparent sheet in outdoor, architectural materials or electronic equipment, and non-food contact packaging.