Synthesis and crystallization behaviors of highly fluorinated aromatic polyesters

Studies on fluorine containing condensation polymers are limited compared to that of fluorine containing addition polymers. In this report, highly fluorinated aromatic polyesters were synthesized by a polycondensation reaction of tetrafluorophthalic anhydride with ethylene glycol. Viscosity, solubility, thermal properties and crystallization behaviors of fluorinated polyesters were investigated using IR, 19F NMR, DSC, GPC, polarized optical microscope and rheometer. The fluorinated polyester is insoluble in most organic solvents, such as acetone, ethyl acetate, chloroform, THF, and trichloromethane. However, it is soluble in highly polar solvents, such as dimethylsulfoxide, dimethylformamide and dimethylacetamide. The fluorinated polyester (o-PETF) is a crystalline polymer with a crystallization enthalpy of 35.2 J/g and a broad crystallization temperature range from 54 to 130 °C. Average crystalline growth rate is 4.2 μm/min at 110 °C in the preliminary 30 min. Spherulite growth was observed at the temperature when the dendrites begin to melt. Crystallization property of o-PETF may be ascribed to the higher mobility of fluorinated polyester chains and dipolar contribution of carbon-fluorine bonds.