Effects of Various 1,3-Propanediols on the Properties of Poly(propylene furandicarboxylate)

Diols or acids with different skeletal structures could be used to polymerize 2,5-furandicarboxylic acid (FDCA) in order to adjust the properties of FDCA-based polyesters. A series of FDCA polyesters with similar skeletal structure as poly­(propylene furandicarboxylate) (PPF) were prepared from FDCA and 1,3-propanediols containing different substituent groups. The effect of substituent groups on the thermal properties and gas barrier behaviors were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), rheological analysis (RA), and positron annihilation lifetime spectroscopy (PALS). The substituent −CH3 significantly influenced the thermal properties of the polyesters, where the glass transition temperature (Tg) and crystallizability increased from PPF to poly­(neopentyl glycol furandicarboxylate) (PNF) and then decreased from PNF to poly­(2-ethyl-2-butyl-1,3-propylene furandicarboxylate) (PEBF). PNF displayed the highest Tg of 70 °C and Tm of 201 °C with a ΔHm of 32.1 J/g. PPF possessed a Tm of 173 °C with ΔHm of 0.9 J/g, while poly­(2-methyl-1,3-propylene furandicarboxylate) (PMF) was an amorphous polyester. The gas barrier properties followed the trend of PPF > PMF > PNF due to the increased β relaxation and fractional free volume (FFV) after the introduction of lateral −CH3 groups