Journal of Chemical Physics, Vol.120, No.11, 5455-5462, 2004
Johari-Goldstein relaxation and crystallization of sorbitol to ordered and disordered phases
The equilibrium permittivity e, and the dielectric relaxation spectra of supercooled liquid D-sorbitol were measured during its crystallization to orientationally disordered or ordered phases depending on the sample preparation procedure at several fixed temperatures up to a period of 6 days. The 8, measurements showed that when the sample was contaminated by a minute amount of crystals, it crystallized to an ordered phase. When the liquid was not contaminated, the sample crystallized to an orientationally disordered phase. When supercooled D-sorbitol was kept close to its T-g, its dielectric spectra did not change over a period of 138.5 h. It was found that the Johari-Goldstein (JG) relaxation rate of the orientationally disordered crystalline phase is higher in comparison with that of the supercooled liquid, the spectrum broader, and the relaxation strength lower. Its glasslike transition temperature is higher than T-g of the liquid. The results on crystallization showed that the structural changes occurring at a temperature where the a relaxation emerges from the JG relaxation affects the crystallization kinetics of the liquid. (C) 2004 American. Institute of Physics.