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

N S K Kumar; G Govindaraj; U Sailaja

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arXiv · 1609.02649

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

N S K Kumar·G Govindaraj·U Sailaja

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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.

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N S K Kumar, G Govindaraj, U Sailaja. 2016-09-09. Molecular motions in glass and supercooled states of clotrimazole studied by broadband dielectric spectroscopy. https://arxiv.org/abs/1609.02649

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