Molecular motions in glass and supercooled states of clotrimazole studied by broadband dielectric spectroscopy

Abstract

The molecular mobility of glassy and supercooled liquid states of clotrimazole is studied using broadband dielectric spectroscopy for a wide range of temperatures and frequency. The dielectric loss data of clotrimazole below T$_{g}$, do not show well resolved relaxation. Above T$_{g}$, dielectric loss show the structural $\alpha$-relaxation which is reformed to shoulder like shape at high frequencies due to the secondary relaxation. The relaxation time of $\alpha$-process, $\tau_{\alpha}$ follows Vogel-Fulcher-Tammann equation. The glass transition temperature, $T_{g}$=296K and fragility index, m=50 are obtained from the thermal behaviour of the $\alpha$-process. At temperature near T$_{g}$ the dielectric loss has Kohlrausch-Williams-Watts stretch exponential parameter $\beta_{KWW}$=0.56. The primitive relaxation time obtained from the coupling model coincides with the experimentally observed secondary relaxation of clotrimazole. Hence the secondary relaxation is considered to be the Johari-Goldstein (JG) process which may be the precursor $\alpha$-process. The value of exponent $\beta_{KWW}$ increases with increase of temperature and scaled dielectric loss do not form as single master curve. The structural relaxation $\alpha$-relaxation and JG $\beta$-relaxation process and its effects in clorimazole is discussed.