Poly(ethylene 2,5-furandicarboxylate) (PEF) is a biobased polyester with high gas barrier properties, tensile modulus, and strength. In PEF chain, in addition to ethylene furandicarboxylate repeat unit, there is also a small amount of diethylene glycol furandicarboxylate (DF) unit which is formed by etherification side reactions. However, the effect of DF unit in a wide composition range on polymer properties is still unclear. In this study, random poly(ethylene-codiethylene glycol 2,5-furandicarboxylate) (PEDF) copolymers were synthesized via melt copolycondensation of 2,5-furandicarboxylic acid, ethylene glycol and diethylene glycol. The copolymers were characterized and evaluated by intrinsic viscosity, 1H NMR, thermal transition, thermogravimetric analysis, tensile, impact, and O2 penetration tests. The copolymers are amorphous in the full composition range. The presence of less than 58 mol% DF unit in PEDFs neither improves the tensile ductility nor deteriorates the oxygen barrier performance, but reduces the glass transition temperature clearly. In comparison with 

poly(ethylene terephthalate), the PEDF copolymers containing <58 mol% DF unit have higher tensile modulus, strength, and O2 barrier properties.