Thermostable block copolymers, 1. Thermotropic poly(ester-imide) block copolymers^†

New poly(ester-imide) block copolymers were prepared by polycondensation of aminoterminated poly(ester-imide) blocks with molecular weights from 700 to 6 000 with terephthaloyl dichloride, isophthaloyl dichloride, 2,6-naphthalenedicarbonyl dichloride, adipoly dichloride, dichlorodimethylsilane or dichlorotetramethylsiloxane as low-molecular-weight difunctional coupling reagents. The poly(ester-imide) blocks were synthesized from readily accessible monomers. Dependent on block composition, molecular weight of the block (block length) and kind of spacer liquid-crystalline polymers were obtained with high thermal stability and solubility in polar solvents, yielding tough films with good mechanical properties. The formation of thermotropic mesophases required the proper balance between the rigid blocks and the flexible, kinked or “crankshaft” spacers.