Synthesis and Thermal Behavior of New Poly(ethylene terephthalate-imide)s

Copoly(ethylene terephthalate-imide)s (PETIs) were synthesized by the melt copolycondensation of bis(2-hydroxyethyl)terephthalate with a new imide monomer, N,N9-bis[p-(2-hydroxyethoxycarbonyl)phenyl]-biphenyl-3,39,4,49-tetracarboxydiimide (BHEI). The copolymers were characterized by intrinsic viscosity, Fourier transform infrared, H NMR, differential scanning calorimetry, and thermogravimetric analysis techniques. Although their crystallinities decreased as the content of BHEI units increased, the glass-transition temperatures (Tg) increased significantly. When 5 or 10 mol % BHEI units were incorporated into poly(ethylene terephthalate), Tg increased by 10 or 24 °C, respectively. The thermal stabilities of PETI copolymers were about the same as the thermal stability of PET, whereas the weight loss of PETIs decreased as the content of BHEI units increased. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 408–415, 2001