Dielectric relaxation and crystallization behaviour of amorphous nilutamide

Abstract

The molecular mobility of glass and supercooled liquid states of nilutamide has been studied with broadband dielectric spectroscopy for a wide range of temperature and frequency. Besides primary $\alpha$-relaxation an excess wing like secondary relaxation is observed. The temperature dependence of structural $\alpha$-relaxation show non-Arrhenius behaviour, and follows Vogel-Fulcher-Tammann (VFT) empirical formula. The glass transition temperature, T$_{g}$=302K and fragility index, m=76 are obtained from the VFT parameters. The structural $\alpha$-relaxation process is non-Debye with Kohlraush-Williams-Watts stretched exponential $\beta_{KWW}$=0.76. Secondary relaxation time of nilutamide coincides with the primitive relaxation time calculated from the coupling model. Hence the secondary relaxation process of nilutamide is treated as the Johari-Goldstein (JG) $\beta$-process, which is the precursor of the structural $\alpha$-process. Recent report on nilutamide indicates the increase of nucleation even below T$_{g}$, however we attributed to the JG $\beta$-relaxation. During the dielectric measurements amorphous nilutamide recrystallizes. The crystallization of amorphous nilutamide has been studied by the isotherm dielectric measurements at T=326K over a period of time. The crystallization follows Avrami equation and the parameters are obtained.