LIQUID-CRYSTAL TRANSITION AND CRYSTALLIZATION KINETICS IN POLY(ESTER IMIDE)S

A series of monotropic liquid crystal poly(ester imide)s (PEIMs) was s ynthesized from -(chloroformyl)phenyl]-4-(chloroformyl)phthalimide and nine diols containing 4-12 methylene units (m). During cooling from t heir isotropic melts, all the polymers underwent a monotropic liquid c rystal transition to form a smectic A phase, followed by a transition to a more ordered structure, which was examined with wide-angle X-ray diffraction, differential scanning calorimetry, and polarized light mi croscopy. The fact that the liquid crystal transition temperatures for some of the PEIMs were close to their glass transition temperatures p rovided an opportunity for the study of liquid crystal transition kine tics in temperature regions close to the glass transition temperature. It was found that when the temperature, and thus the molecular mobili ty decreased, the transition time increased despite the fact that this transition is close to equilibrium. The crystallization kinetics of P EIM(m)s from both the liquid crystal phase and the isotropic melt were also studied. In PEIM(m=even)s (except for m = 4), two different orde red structures can be formed. One is a crystalline phase formed direct ly from the isotropic melt, and the other is a highly ordered mesophas e having a hexagonal-like packing develop from the liquid crystal stat e. Only one crystal structure in PEIM(m=odd)s is observed. Special att ention has been paid to the effect of the presence of liquid crystal o rder on the crystallization kinetics. The pronounced acceleration of t he crystallization was observed whenever this was preceded by liquid c rystal formation, an effect pertaining within a wide temperature range from close to T(m) down to T(g).