克霉唑玻璃态和过冷态分子运动的宽带介电谱研究
Molecular motions in glass and supercooled states of clotrimazole studied by broadband dielectric spectroscopy
摘要：
用宽带介电谱研究了克霉唑在宽温度和频率范围内的玻璃态和过冷液体态的分子迁移率。克霉唑在T $_{g}$以下的介电损耗数据未显示出良好分辨的弛豫。在T $_{g}$以上，介电损耗显示结构$α$-弛豫，由于二次弛豫，该结构在高频下被改造为肩状形状。$α$过程的弛豫时间$τ_α$符合Vogel-Fulcher-Tammann方程。从$α$-过程的热行为获得玻璃化转变温度$T_{g}$ = 296 K和脆性指数m = 50。在接近T $_{g}$的温度下，介电损耗具有Kohlrausch-Williams-Watts拉伸指数参数$β_{KWW}$ = 0.56。从耦合模型中得到的原始弛豫时间与克霉唑的二次弛豫时间一致。因此，二次弛豫被认为是Johari-Goldstein（JG）过程，其可以是前体$α$过程。指数$β_{KWW}$的值随温度的升高而增大，标度介电损耗没有形成单一的主曲线。讨论了氯利马唑的结构弛豫过程$α$-弛豫和JG $β$-弛豫过程及其影响。
英文摘要：
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 $α$-relaxation which is reformed to shoulder like shape at high frequencies due to the secondary relaxation. The relaxation time of $α$-process, $τ_α$ 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 $α$-process. At temperature near T$_{g}$ the dielectric loss has Kohlrausch-Williams-Watts stretch exponential parameter $β_{KWW}$=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 $α$-process. The value of exponent $β_{KWW}$ increases with increase of temperature and scaled dielectric loss do not form as single master curve. The structural relaxation $α$-relaxation and JG $β$-relaxation process and its effects in clorimazole is discussed.
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