| 초록 |
The phase transition, crystallization kinetics and morphology of monotropic liquid crystalline poly(ester-imide)s are investigated by synchrotron X-ray diffraction, differential scanning calorimetry (DSC), polarized light microscopy, and transmissionelectron microscopy (TEM). Synchrotron X-ray diffraction and DSC results show that the poly(ester-imide) with methyl side pendant group (10M) exhibits monotropic nematic and smectic A phases upon cooling from the isotropic melt, followed by a crystalline phase (crystalE structure). The results of isothermal crystallization kinetics show that the crystallization rate is faster in smectic phase than in nematic phase and the slowest in isotropic phase. It is found that the crystallization in nematic phase leads to the lamellar decorated disclination structures upon TEM observation, indicating that the enhancement of nucleation dominates the acceleration of crystallization. Poly(ester-imide) without side pendant group (10H) forms only crystalline phase upon cooling. However, the air-quenched sample shows a thread-like texture. TEM observation further reveals the trace of nematic disclination structures, confirming that the crystallization proceeds through nematic phase. In contrast, the sample, cooled with a slow cooling rate of 5 C/min, exhibits the spherulite structure of. The morphological variation of the poly(ester-imide)is discussed based on the competition between primary nucleation and growth of crystal.
|
