METASTABLE PHASES IN KINETICS OF PHASE-TRANSFORMATIONS IN THE FROZEN LIQUID-CRYSTAL 4-ETHOXYBENZYLIDENE-4'-N-BUTYLANILINE

The nematogen 4-ethoxybenzylidene-4'-n-butylaniline gives by fast cooling a frozen phase called C1 different from a glassy nematic state. The X-ray diffraction spectra of a non-aligned sample and a sample aligned by a magnetic field show that the C1 phase is a monolayer smectic phase: molecules are inclined to the normal of the smectic planes by an angle of 35-degrees +/- 5-degrees. On reheating we obtain metastable phases more and more ordered; those phases C2 and C3 are crystalline. The kinetics for the metastable phases correspond to a nucleation growth process of the same type (n = 2) for the two transformations C1 --> C2 --> C2. If we assume a thermal process the growth is monodimensional.