Modification of poly(ethylene 2,5-furandicarboxylate) (PEF) with 1, 4-cyclohexanedimethanol: Influence of stereochemistry of 1,4-cyclohexylene units

Poly(ethylene- co -1,4-cyclohexanedimethylene 2,5-furandicarboxylate) (PECF), with different contents of trans - or cis -CHDM isomers, was synthesized to investigate the influence of CHDM configuration on its properties. Before properties investigation, their chemical structures , composition and molecular weight as well as molecular weight distribution were determined by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Their thermal and dynamic mechanical properties as well as barrier properties were measured by differential scanning calorimeter (DSC), thermogravimetric analyzer (TGA), dynamic mechanical analysis (DMA) and gas permeability tester. Results showed that the PECFs could be changed from amorphous polyester (PECF-trans 25) to highly crystalline polyester (PECF-trans 98) by increasing the content of trans -CHDM from 25% to 98%. The melting temperature of PECF-trans 98 was as high as 252 °C and its crystallization half-time was only 15 s. Besides the tensile modulus and strength, the O 2 and CO 2 barrier property of PECFs were all increased with the increasing content of trans -CHDM. When the content of trans -CHDM was higher than 55%, PECFs showed excellent gas barrier properties, which was better or comparable to those of PEN and PEI.