邻苯二甲酸二甲酯系材料中α-弛豫的降温介电谱测量与分析

Measuring and analyzing the cooling dielectric spectra of the cx-relaxation in dimethyl phthalate series materials

对邻苯二甲酸二甲酯（dimethyl phthalate）、邻苯二甲酸二乙酯（diethyl phthalate）、邻苯二甲酸二丁酯（dibutylphthalate）和邻苯二甲酸二异辛酯（dioctyl phthalate）系列材料中,α-弛豫的降温介电谱进行了测量,得出了相应材料α-弛豫的平均弛豫时间τ_α~a妄随温度T的变化关系.通过τ_α~a量的实验结果与经验的vogel-Fulcher-Tammann）定律τ_α~a=r_α~Oexp（A/（T-T_o））的拟合,获得了上述系列材料的τ_α~a,A和T_o.分析发现,随邻苯二甲酸二甲酯系列分子侧链中碳原子数目n的变化,材料的τ_α~a,A,T_o和T_g表现出一定的规律性,具体为随n的增加,即分子内部自由度的增多,A和T_g都表现出近乎相同的先减后再增的趋势,而1/τ_α~a和T_o则表现出基本相同的先快速减小,然后保持基本上不变的趋势.

The cooling dielectric spectra of the a-relaxation in dimethyl phthalate,diethyl phthalate,dibutyl phthalate,and dioctyl phthalate series materials are measured,and the average relaxation time of theα-relaxationτ_α~a as a function of temperature T is obtained.By fitting theτ_α~a data to the empirical Vogel-Fulcher-Tammann lawτ_α~a =τ_α~0 exp（A/（T-T_0））,the values ofτ_α~0,A and T_0 of the series materials are obtained.The results ofτ_α~0,A,T_0 and T_g show some variation regularities with the carbon number n in the side-group of dimethyl phthalate series molecules.And specifically,with the increase of n,the internal degrees of freedoms of the molecules,A and T_g indicate almost the same tendencies,i.e.first coming down and then going up,while l/τ_α~0 and T_0 have quite similar behaviors,i.e. first reducing rapidly and then keeping at near constant values.