Microscopic observation of a peculiar crystallization in the glass transition region and β-process as potentially controlling the growth rate in triphenylethylene

The dielectric relaxation times of triphenylethylene (TPE) were measured in the supercooled liquid state, and it was found that TPE is one of fragile compounds similar to o-terphenyl. The peculiar crystallization proceeding in the glass transition region was studied by microscopic observation, and found to proceed as the crystal front advances into the liquid phase. The crystal-growth rates increased with increasing temperature above 237 K but suddenly ceased at 257 K, as observed in o-terphenyl. It is discussed that the crystallization is based on the homogeneous crystal nucleation in the supercooled liquid, that the beta-process controls the growth rate, and that the coincidence of the molecular orientations in the interface between the preexistent crystal and crystal embryo is a key factor to macroscopic appearance of the crystallization. (C) 1999 Elsevier Science Ltd. All rights reserved.