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 mon omer, N,N'-bis[p-(2-hydroxyethoxycarbonyl)phenyl]-biphenyl-3,3',4,4'-tetrac arboxydi- imide (BHEI). The copolymers were characterized by intrinsic visc osity, Fourier transform infrared, H-1 NMR, differential scanning calorimet ry, and thermogravimetric analysis techniques. Although their crystalliniti es decreased as the content of BHEI units increased, the glass-transition t emperatures (T-g) increased significantly. When 5 or 10 mol % BHEI units we re incorporated into poly(ethylene terephthalate), T-g increased by 10 or 2 4 degreesC, respectively. The thermal stabilities of PETI copolymers were a bout the same as the thermal stability of PET, whereas the weight loss of P ETIs decreased as the content of BHEI units increased. (C) 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 408-415, 2001.