| Abstract: | A novel side‐chain liquid‐crystalline polyimide (SLCPI) was prepared via copolycondensation from 3,5‐diamino‐benzonic‐4′‐biphenyl ester, 4,4′‐diamino‐ biphenyl ether, and 3,3′,4,4′‐oxydiphthalic dianhydride. The energy‐minimized structure and liquid crystallinity of SLCPI were investigated by molecular modeling, differential scanning calorimetry (DSC), wide‐angle X‐ray scattering, and polarized optical microscopy, respectively. The results indicated that this polyimide (PI) with side‐chain mesogenic units exhibited a nematic NI phase. Because of the in situ self‐reinforcement of side‐chain mesogenic units, the improved tensile strength and modulus of PI films reached 270% and 300%, respectively. The coefficient of thermal expansion of films decreased by 40%. DSC and thermogravimetric analyses indicated that the phase‐transition temperature of SLCPI was above 240 °C, and the 5% weight‐loss temperature was above 520 °C. Moreover, copolycondensation of two diamines with dianhydride and incorporation of pendent mesogenic units diminished the regularity and symmetry of main chains; as a result, SLCPI exhibits good film processability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 554–559, 2003 |
